Long story short: Usability on most FOSS is shit.
I think I can also explain why: Many many FOSS projects are heavility dominated by programmers. Other rules, like UI designers, are often lacking. And if programmers design an UI, usability is usually shit because programmers make the wrong assumptions about their user. UI design is a separate skill that needs to be learned separately.
FOSS projects seem to generally have a shortage of non-programmers in their teams. The solution? Convince non-programmers to join us.
The free software movement was fairly successful in making a healty number of programmers join it. However, finding people skilled in any other task, anything that is not programming, is still much tougher.
As for postmarketOS: As a developer, I'd say making this process run out-of-the box is a challenge, even if you have money. postmarketOS is something the user is supposed to install on their smartphone to replace an existing OS. The challenge comes from the fact that postmarketOS devs have no freaking idea on which device YOU want to install it on. From a programmer viewpoint, you would have to test the install process on loads of loads of different devices with all their different hardware, some of which just don't work in Linux at all because no Linux driver exists at all, or the only Linux driver that exists is 3rd-party, proprietary and shit. The more devices you want to support, the harder it will become, because it just would eat so much time to test every possible hardware. I'm not saying this task is impossible, but it will definitely be a lot of work. I hope they at least wrote down somewhere which devices are supported; this question is very important.
When installing a Linux-based OS on any device, the hardware question is very important. You need to know if the hardware in your device is even supported by Linux. Otherwise, you can already forget it. You might find some 3rd party drivers somewhere but those are usually shit and installing and maintaining them is definitely a nightmare, based on experiene. Good libre drivers are usually already included in Linux itself, so the best way to install Linux is to first find a device/hardware that Linux supports. I think “missing hardware support” is still the biggest roadblock.
I think for smartphones, the only real solution to make FOSS OSes practical is to sell those devices with a libre OS pre-installed. There are some manufacturers that do this already, but they are rather small, very few people know them, so you have to specifically search them. FOSS on smartphone is NOT mainstream at all (it should be)!
Installing a new OS on a smartphone is, in my experience, never a foolproof task, it generally requires a deep understanding of how things work, and patience. However, a manual can help here, IF the manual is actually giving the correct instructions. I think far too many software projects (not only FOSS ones …) don't test their documentation, and broken installation instructions are left there for years because nobody checks if they actually work.
Your experience suggests there might not have been a proper installation manual. Those are questions that should have all been covered in a proper manual (you DID look for a manual, right? RIGHT???
). Yeah, shitty or missing documentation is another problem in some FOSS. Not all FOSS, mind you!
On the other hand, I have to defend postmarketOS here. This system is currently in the ALPHA version now which is clearly stated on their homepage. This means it's not even finished, so it's only for demonstration purposes right now; many bugs, rough edges, missing features, and many other problems are expected. So you have no right to complain about bad usability of postmarketOS specifically.
Maybe come back when they release version 1.0.
Nobody deserves such pain to just use the device they've paid their money for.
Now you're just being mean. You clearly can't blame the smartphone manufacturer for a bad OS if you install a 3rd party OS on their device. The blame only belongs to them if the pre-installed OS is broken/bad, or if they officially support the OS you chose. I highly doubt postmarketOS is officially supported since it was not pre-installed.
However, I DO think they (and the traders) deserve blame when they only sell their devices with proprietary software pre-installed, so the only option that buyers have is proprietary, and no FOSS. FOSS must become more mainstream, and pre-installing it is a big first step.
You need to remember, FOSS is, at its core, a political movement. And yes, a lot of FOSS is still shit, and we have many usability problems, and other problems. Granted. But we also are lacking greatly in manpower, we're just a small puddle in an ocean of proprietary software. So we're simply at a huge disadvantage … yet. Convincing more people to join our side is still a very very important challenge of the free software movement.