This sounds a lot like the Flattr model - a service that had its moment in 2010/2011, but ultimately failed: https://en.wikipedia.org/wiki/Flattr
Payments are a challenge, with processing fees and taxes in an international context, small sums don't work out well - there's a reason why services like Liberapay push you to do bigger amounts at one time instead of small amounts at multiple points in time.
Honestly - using Sxmo on a PinePhone Pro is about as hard-core as you can go beyong building your own thing from scratch.
Ubuntu Touch on Pixel 3a, or Sailfish X on a supported device or a Librem 5 with PureOS even is a lot less geeky and more approachable thing.
The Shift6mq is a great phone, no doubt about that. Glad you like it! It's a pretty main-stream design hardware-wise though, compared to how the Librem 5 is built, see https://lemmy.ml/comment/2645546 - that does not make it worse device though.
My only point was that I don't see how people arrive at "Purism is a cultist org" when some rando writes a stupid email to a YouTuber who is not part of that organization.
Regarding the investment in software: It's not just Phosh, it's libhandy (and libhandy-4/libadwaita), the initial work on adaptiveness in GNOME apps (which makes GNOME Shell on Mobile such a slam dunk), the modem manager based telephony stack (instead of dealing with weirdly patched forks of ofono, a project originating from Nokia/Intel's Meego), and more. So even if you are not a fan of Phosh, which is perfectly fine, you may still benefit from Purism's effort and most certainly the community efforts that took this work and build upon it/brought it to other UIs and hardware.
I maybe an old fool, but I still credit Purism for starting the Librem 5 effort in a time shortly after Canonical had announced it would no longer develop Unity 8/Ubuntu Touch, Jolla were struggling, and other efforts had long been dead.
Edit: One thing I forgot: The people that Purism payed/pays for Librem 5 software work are usually community members, BTW.
So you're blaming a company for a person not on its payroll writing a weird and dumb email? Ok.
They did do a "slap a logo on things"-thing with FOSS Android apps for their librem.one service. On the other hand, they do actually pay for software development for the Librem 5 in a way that helps the entire #linuxMobile ecosystem - a PinePhone or a Snapdragon 845-powered Android phone running postmarketOS would be way less useful without Purism's investment. It's all quite grey.
Yes, the Librem 5 is expensive and Purism treat consumers poorly.
But, the comparison and the focus on pure specs make it seem that you don't understand the appeal of the product, which is to run a GNU/Linux stack on a phone with a very-close-to-mainline kernel. Among the devices you compared the Librem 5 too, the only one that's comparable is the PinePhone Pro (yes, the others support Ubuntu Touch, but they are essentially standard Android hardware featuring a Mediatek or Qualcomm SoC. The vendor kernel is then being used with a compatibility layer to run Ubuntu Touch on it.
The PinePhone Pro (as the only other mainline smartphone in your comparison) is significantly cheaper, but that's in large part due to PINE64's modus operandi: They supply hardware, and the community makes that hardware usable by supplying the software. This model has worked okay for the OG PinePhone, may be due to the Community Editions, where PINE64 partnered with distributions/software projects, but it has not worked so well for the PinePhone Pro. The PinePhone Pro also has - depending on how you want to spin it - a too power hungry SoC or a undersized battery. Thanks to standby, it can last a day, but you can't really use it for much during that day then - e.g., browsing the web rapidly drains the battery. Also, without Purism's efforts, there would be way less user space software to make use of the device.
The Librem 5 is not without flaws, it's a really complicated hardware device (they were aiming for some FSF stamp of approval) - while the (socketed) 4G modem has GPS support, Purism also added a dedicated chip for that so that you can navigate while the LTE unit is "killswitched off". The NXP i.MX8M only has Cortex A53 cores, and the GPU is not amazing, either (at the time when design decisions were made, it was the only GPU with decent blobless mainline driver support though), but at least the battery is large enough to make the Librem 5 a phone I can reasonably use as a daily driver these days.
Regarding the Liberty Phone: I hate the name, but given that this is just the Librem 5 USA with as much RAM as the SoC supports and a larger eMMC, there's no technical excuse to delay that product, as these hardware changes are very, very minor.
I use Evolution for email (which ... well, is somewhat doable with scale-to-fit), and it notifies me about contact birthdays.
Regarding Beepy: I really tried, but ... compared to that, PinePhone was easy to get to a somewhat works state in mid 2020. See https://linmob.net/enter-beepy-esc/#flaws