There might be something wrong with this application, because others app can be upgraded, but when I try to upgrade QKSMS, Apps crash just after download. (and of course do not upgrade QKSMS)
Then, I was able to remove QKSMS, but when I try to install it again, Apps crash again. So it looks to me that Apps refuse to install or upgrade QKSMS.
an idea ?
/e/ version is 0.13-2020121490326
android 9
lineageos API llama(9)
on a samsung S8
Not only, it seems.
I uninstalled QKSMS and now I’m unable to install it again (same crash, when the download reaches 100 %). I’m now stuck with the similar-but-less-pretty default fork thingy. 
Edit: Wow I’m kinda dumb; the topic creator said basically the same thing. Still, at least this shows it’s not an isolated problem. 
(Faiphone 3+, Android 10, /e/ build of the 2020-12-14)
Let’s hope that Apps will still update itself to solve this.
Can you install F-droid from Apps and install QKSMS from there?
I ended up doing this, yeah, thanks. F-droid seems to work pretty well. It even fetched me a vlc update that Apps didn’t have yet, as well as something for OpenKeyChain. 
I deactivated auto-updates in Apps to make sure I would not get both Apps and F-droid trying to install the same thing at the same time or whatever.
The only unexpected thing I got was when switching back to QKSMS as my default messaging application: a never-seen-before popup saying something like “Yo, if you have a screen locking thingy and reboot your phone, the application you just selected won’t be able to start until you unlock your screen”. Weird. Didn’t have that the first time I switched to this app. 
Still, I hope Apps will have increased stability in the future, or at least provide more info than just closing brutally. I suppose there are logs somewhere, but still.
Haha my thoughts exactly; this could escalate into a nightmarish chicken-and-egg problem. 