That's actually quite cool to know.
I've always wanted to make my own Cola, especially since I can't tolerate even small amounts of caffeine. Thanks!

Either Localsend, if you're only interested in that one function, or KDE Connect for the ultimate experience.

GrapheneOS is probably the best option out there.

As you said, it's only for Pixels currently, because

1. They are more secure than most other phones. They have some kind of chip built in that makes them superior. I don't know the specifics, but other commentators might add some information if needed. Something with encryption if I remember correctly. The GrapheneOS team is a bit ...picky... when it comes to security, and most other phones don't reach their requirements for a secure device.
2. Google is one major contributor to Android, and their phones are fine tuned to work perfectly with it. Other manufacturers' phones feel less polished.
3. It's easier to maintain one line of devices that are very similar, instead of keeping hundred phones up to date and secure. Pixels are similar to iPhones, they get updated almost simultaneously and are similar. If you now add a phone from a different line, e.g. a Fairphone or Nothing Phone, things get more complicated. If you look at Calyx (more onto that later), the FP4 caused quite some headaches for the dev team.

Pixels are cheap(ish) for what you get, and I believe Google makes them so cheap because 99% of users don't care which ROM/OS is installed. Those are the advertisment-cows that will get milked. If you buy a Pixel and install a custom ROM on it, they will loose money.

My experience with GrapheneOS has been great. My Pixel 5 hit EOL a while ago and still gets maintenance updates almost weekly.
Many security additions are overkill for me, but quite some make a lot of sense.

I used CalyxOS for a year too, but now that I don't get full updates anymore, I don't feel safe anymore with it.

I think GrapheneOS is technically superior to Calyx, especially due to the sandboxing they do. MicroG has full root privileges and can do with your phone what it wants, while also breaking some apps due to missing dependencies. If you choose to enable Play Services on GrapheneOS, they are user level and heavily restricted, and only you decide how much access you want to give them.

Regarding Calyx, since they don't limit themselves as much in terms of security, they also offer a ROM for the Fairphone. Maybe check that out too.

DivestOS also seems to be a good option. AFAIK it's based on LineageOS and supports a lot of devices, while being more secure than LOS.

Regarding Linux phones, I don't have any experience with them. I tried Phosh (Mobile Gnome) on an exhibition a while ago, and it felt great and interesting, but from what I've heard, they are nowhere as good as Android.

My personal ranking:

1. GrapheneOS on a Pixel. Get an used/ refurbished device if you don't want to support Google. Best price-performance ratio, great OS, and very good hardware (battery life, camera, etc.)
2. CalyxOS on a Fairphobe. Modular device with good repairability. Nowhere near as good in terms of what you'll get for your money. Better security than 95% of other phone ROMs, oh, and you can just swap your battery in seconds if you want that :D
3. DivestOS on a random supported phone, e.g. a China device. Nowhere near as sustainable (short lived update support, no spare parts, etc.)
4. Linux phone. Only a good option for a tinkering device right now imo.

Short answer: use uBlue.

Longer answer:

Even though uBlue is technically "downstream", it also isn't. uBlue builds its' packages automatically, and you are never more than a few hours (1 day max for huge updates) away from upstream. It feels more like "sidestream" (if that word exists?).

One reason it exists is, as you already said, because layering takes quite some time.
At least I personally don't wanna use stock Fedora (Atomic) and would install some codecs, tweaks and such anyway, and uBlue does that already for me.
Update time doesn't matter anymore for me, because uBlue updates itself automatically in the background. Silverblue doesn't do that afaik.

Depending on how "custom" your system should be, you can take a look at the uBlue builder, where you can create your own image based on already existing ones if you like.

The cool thing about Fedora Atomic is, that you don't have to stick to anything. If you don't like something anymore, you can rebase in less than two minutes without any hassle and jump from image to image, no matter if it's an official one (e.g. Silverblue) or some obscure uBlue image.

This may be an unpopular opinion, but you can use pretty much anything you like, as long as it isn't brand new or extremely old.
Even stuff with Nvidia GPUs and stuff.
Even MS Surface devices work decently.

Thing is, for a really smooth experience, where you don't feel like a second class citizen, and everything works ootb, proper support is advantageous.

I have a Dell XPS laptop, and it works fine. Sometimes, the WiFi switches itself off, and I have to restart the connection, but other than that, everything is flawless.
Thinkpads are great too, since they are also used heavily in offices, where they get thrown out or sold cheaply. Maybe ask there.

I personally would recommend something that you can repair yourself, or at least change the battery and memory.

Yes, just yes. Try it. If you want, I can elaborate further.

I've been using it for about a year now, and I just can't imagine going back to a traditional mutable distro.
I've never encountered any personal issues (capabilities, convenience, breaking things, annoyances) as a casual user.

I would recommend you Bazzite, but you can always just rebase to Aurora if you want, it literally takes just 2 minutes.

Just search for Fedora Atomic here on this community, and you will find dozens of great experience reports.

Go with Bazzite instead.

The Nvidia drivers come pre-bundled with your install and are baked into the image itself.
The good thing is, they won't break, and if they should, you can just roll back to yesterday's image by just rebooting. It's extremely reliable and lets you just dive into your optimal gaming experience straight away.

Don't use Manjaro. The dev team is very sketchy and it's a very unreliable distro. If you really want Arch, for whatever reason, use EndeavourOS. I personally don't like the rolling release model and find Fedora (Bazzite) just right. If I need something from the AUR, then I use Distrobox.

PopOS is too old for me, and isn't evolving at all right now. I would skip it until Cosmic is ready.

There are a few "grandfather"-distros out there, for example Debian and Arch. They've been around for a few decades now.

Then, they got kinds, because some people said "I don't like xy, I will do it better", but granddaddy disagreed, so they split apart.
That's what Ubuntu is to Debian for example, that's why Ubuntu is Debian-based. They are related to each other (e.g. the same package manager), but differ in some things (e.g. update cycle).

This cycle of forking continues, that's how Mint got there for example. Mint is based on Ubuntu, and Ubuntu is based on Debian.

But nowadays, the gap between distros gets smaller, with things like Distrobox, Nix, Flatpaks, and more. I wouldn't mind working with a PC that has Mint on it instead of Fedora. Sure, there are reasons why I prefer one over the other, but in the end, they're all the same.

One example I can think of where the base matters, and not the package manager, is when adding an user to the sudo group. RedHat distros need another promt than Debian for example.

But other than that, the thing that defines a distro are the packages, they make a distro unique.

Yeah, definitely, especially at work.
It really helped me to switch off my "work brain", because I know, that everything I did today is written down, and I don't have to keep things in my mind anymore after work. Doing that was a blessing for my stress level and mental health.

It also gives me the edge above my colleagues that I "remember" everything I did in the last months, which is nice when my boss wants to know details of a project I did a year ago.

I basically can't even remember what I did 5 minutes ago (ADHD says hello), but I know exactly where I can find that knowledge. This frees up my working memory (psychological term, not related to work) immensely. It's basically like transfering more tasks onto your hard drive instead of keeping it in the RAM.

It's also great to give me an graphical overview of all I think and work on all day, and unveals connections I never thought of between different topics.

For private use, it's also great as a journal, though I gave up on that because I'm too busy for it and it cost too much time in my everyday life. But I still use it daily for normal note taking, e.g. results of some experiments at home, hobbies, thoughts, and much more.

Logseq.

AUR for niche stuff, Flatpak for everything else.

I personally prefer Flatpak because:

• It's simple
• It's the recommended way of installation for most distros, especially image based ones, like Fedora Atomic for example
• It's accessible for everyone more easily
• It works most of the time

I use the AUR in a Distrobox container for software I can't find any other installation method. For me, it's to cumbersome to hop into the terminal and proceed with the installation.
For Flatpaks, it's just one click and it's done.

Because it's outdated. They are a lot of work and can cause package conflicts or errors, making the whole system less reliable.

If you need something, that's not in your package manager, then use Distrobox and create an Arch container, and use the AUR for example.
You can export the program after installing, and it integrates better into your system.

By doing that, the devs have to do the work only once and you will have less problems.