It's different though, you swipe to get to the other characters instead of clicking the button more often. T9 was awesome in its time, but it also kind of relies on a dictionary, like the swiping on "standard" smartphone keyboards. In ThumbKey you type every single character, but it is fast, if you internalize the layout.
ThumbKey made the difference for me. Completely new way to define touchscreen keyboards, but after some months now, I can type blindly on a touchscreen 👍. Caveat: in the beginning typing will be very, very slow.
Family is happy with Matrix (Synapse) and Element as clients. Have members with iOS and Android, smooth experience for all users. But, to be fair, I do have easy users: they basically just send texts, emojis and an occasional picture.
I did not like the admin side of things too much so far, but I recently migrated to a Docker setup, which seems easier to maintain.
I don't know whether that has to do with anything, but interesting trivia nonetheless: 4 is an unlucky number in China, because it sounds similar to "death".
Years ago I tried Snipe IT. As your examples seem to be focused on household and grocery stuff, Snipe IT might be overkill, but according to documentation it supports SAML at least.