SUMMARY The fdroid and nightly repos here: https://cdn.kde.org/android/ have very frequent updates and also many bugs and crashes that occur with newer versions. I also found the "stable-releases" repo (https://cdn.kde.org/android/stable-releases/fdroid/repo), but sadly it does not seem to contain many packages. I would like to have stable-releases for all android compatible packages available.
We only add apps to the stable repository when they are somewhat stable/releaseable. That's not the case for all apps, so it has to be a case-by-case decision