My Monoprice (UC-Logic) PF1209 tablet has pen pressure in some other programs but not Krita. This is in KDE Neon with both default drivers and downloaded ones.

Here is all the troubleshooting and information I could gather, including what the FAQ instructed:
https://hastebin.com/gozayahale.txt

I really hope I can get this working. I can't get another tablet right now and would hate to have to settle for another program that just wouldn't be as good.

You can list the drivers you mentioning before ruling out things, by "default" you mean libinput, evdev or digimend provided from a repository?, and same for the ones you download and how where they installed (usually the modules in the drivers require a rebuild of the linux image and thus a restart, although you probably already knew.).

Have you have more than one installed? (could cause conflict), did Krita worked before in the system in question or is the first time you try it in that specific system?

According to the digimend website your tablet is supported and I don't think they drop models with new versions. Make sure you don't skip any step in the instructions.

Also KDE Neon may be the latest in KDE but is a *buntu non the less, may be an outdated library that doesn't relate to kde but to inputs in general, have you try a live image with another distro? (something new including the core system, just for a test).

Just trying to get more info from you before you get real help from the connoisseurs

I was confused at first which drivers were "default" but I figured out both evdev and libinput were installed. I uninstalled digimend and evdev, rebooted, and now it works.

Thanks for the help.

I wonder though, with some programs working and others not with both evdev and Digimend, is the problem then in Krita? I had not installed any other tablets or other input drivers not mentioned already, it's a fairly fresh system I wouldn't expect conflicts on.

Leaving libinput on its own was the best call imho, (as is the new defacto driver), is not a drawing tablet dedicated driver but rather contains tested and proved code from digimend, (or so I was told), and its in any new system a replacement for evdev driver, luckily for now the only you may need*.

I'm not totally sure about the underground mechanics of all of these programs, but is known (based on others comments) that programs like mypaint or gimp can pickup pressure by different means, while Krita follows (or I should say, receives) a "true" pressure, thus as it is right now, *if you can get pressure on all your programs, it means you have the correct setting system wide and libinput is working as it should. Someone else may be able to correctly explain this as I haven't had the time/head to fully grasp it, I myself at some point have the same situation as you (couple of years back though) thus had a slightly idea of the possible issue, Either case I'm glad is working now, just keep notes for future reference of what works.