alternativeto.net is great for finding these

MakeHuman is a 3D character creation software designed to simplify the creation of virtual humans through a graphical user interface. The software allows users to create realistic human characters by adjusting parameters like gender, age, height, weight, and ethnicity through slider controls. Characters can be customized with clothes, hair, poses, and materials from the built-in library and exported to 3D soft, like Blender.

https://static.makehumancommunity.org/makehuman.html

https://github.com/makehumancommunity/makehuman

Logseq: note-taking and knowledge management application that supports Markdown and Org-mode syntax, featuring powerful linking, block-based organization, and full local data storage for privacy

FanControl: superb PC fan manager with custom temperature/fan speed curves and the options to combine sensors whatever way you like

Warzone 2100 https://wz2100.net/

The first commercial video game to be released in the GPL

OsmAnd: This map application is popular enough that it probably doesn't need mentioning, but good golly is it a powerful tool. Great options for downloading maps and having them offline, and while the car navigation might be missing one or two key features that you'd expect from proprietary alternatives (like live traffic), the sheer amount of detail that has been crowdsourced is mindblowing. There are a wealth of trails and cycle routes, low level details like park benches, bridges, and lookout spots, and the various map profiles you can build are very customizable. I'm personally a huge fan of the trip recording plugin for tracking all my hikes, runs, bike rides, canoe trips, and even swims.

PairDrop like Localsend or Airdrop but working on anything that has an internet connection and a resonably new web Browser! You can share files even when on different networks, by pairing devices. Works like a charm.

NextCloud - Self hosted personal cloud solution that you can run on Docker or bare metal.

https://nextcloud.com/

wezterm: A GPU-accelerated cross-platform terminal emulator and multiplexer written by @wez and implemented in Rust

This is my favorite terminal emulator and very configurable with lua.

Varia is a download manager written using GTK4. Simple, easy, and best of all speeds up downloads significantly on most sites. There also is a extension for Chromium and Firefox, but I haven't tried them.

ShareX, one of the best Screensho/cast productivity tool, edt tools, OCR, QR codes, scrolling capture, color picker......, storing locally, uploading captures to hosts, sharelink in clipboard. Complement with right click extension for Firefox and Chromium

Sadly Windows only

https://getsharex.com/

https://github.com/ShareX/ShareX

I already made a list

Kodi multimedia center.

Learned about the mentos thing in 2006. Saw a list of things to flavor coke. This was #4 on the list and I decided to try it (yay mint coke) - at a dollar tree parking lot, in my car. Went off in my mouth and I maintained the pressure until I got the door open and my head out. Thankfully little mess on me or the car. Learned the internet can be full of sneaky assholes that day.

fzf fuzzy finder. Great tool to quickly find those files you were looking for.

Librera (android pdf+ reader).

I spend a lot of time reading pdfs on my phone, this has done an excellent job. Well featured, responsive, and seems respectful of the battery.

Ads or payment if you buy from the playstore, but free on F-droid and source code is here.

tomb: Tomb is a minimalistic CLI based hidden file encryption tool based on Linux dm-crypt and LUKS.
In addition to its cool ass name, it also has a GUI that's called Mausoleum.

aria2. From the website:

aria2 is a lightweight multi-protocol & multi-source command-line download utility. It supports HTTP/HTTPS, FTP, SFTP, BitTorrent and Metalink. aria2 can be manipulated via built-in JSON-RPC and XML-RPC interfaces.

krename is another excellent, but not as well known as it should be, KDE app.

krename can rename files and directories, and directories recursively, to almost anything. You can rename:

• using information from the files or about the files (image info, date / time info, etc)
• with templates (like #### for incrementing 0001, 0002, 0003, etc)
• by adding parts of the original file name (first three characters then the last 4 characters, for example)
• using find and replace (spaces to underscore, remove special characters, etc), including regular expressions
• by changing case

or with a mix of everything.

krename has a simple mode and an advanced mode for renaming, so you don't have to jump into the deep end with the features.

You do have to be careful with some of the file info functions - it will happily try to rename a movie or a pdf with (non-existent) image EXIF info, for example. That would result in a file with a name you did not intend.

GrayJay platform player. I use it for youtube only but it has many sources.

Grayjay enables you to create and watch video content in your own terms, fully retaining ownership and having control over what you watch. Your content on your terms

https://grayjay.app/

https://gitlab.futo.org/videostreaming/grayjay/

(Not to poop on NewPipe, but this app is better in my opinion, I swapped after their player was bugged for me and I got a bit annoyed on the devs response to not adding SponsorBlock (you can say no to a feature ofc, but he decided to add reasoning that was bad))

Restic, a reliable backup solution.

OONI probe, a tool to test the censorship of wifi networks

eldood: lightweight tool to find dates where everyone is free.

Zulip: An open-source team chat platform with topic-focused threaded conversations.