OSCampus Compat is almost entirely install-time and post-update workflow. These are the repeats administrators forget until lesson edit fatals again.
Install OSCampus, back up the site, install Compat, read install messaging, test lesson create and edit on staging, then promote confidence to production the same way you should have been doing anyway.
Update OSCampus, reinstall Compat immediately, clear opcode cache, open one lesson for edit, confirm no trait property fatal. If fatal returns, confirm reinstall actually ran and check whether AbstractBase.php on disk still shows the typed app property fix.
If uninstall cannot restore because someone deleted AbstractBase.php.rca-orig, restore AbstractBase.php from site backup or reinstall stock OSCampus files for that component version. Do not guess partial edits into AbstractBase.php.
Uninstall when you no longer need the shim, for example when OSCampus vendor ships a native PHP 8 fix and you verified lesson edit without Compat. Uninstall with backup present restores vendor file from .rca-orig. Retest lesson edit after uninstall.