Ok, so while running omv-engined -df I was able to login. No notice worthy errors in the terminal, btw. The only plugin's I had installed where the OMV Extra's repo, Docker and Let's Encrypt. And although they're still running in the background (I'm able to access all my docker containers through their Web GUI) OMV doesn't see them i.e. I cannot access their config screens from the OMV backend.
So, I re-installed OMV Extra's, Docker and Let's Encrypt, but now when I access the config screen I continuously get the error: RPC service 'OmvExtras' not found.
What is this RPC and how do I sync it up to its previous state?
(The rest of my settings (shared folders, etc.) are intact, though. So why does RPC seem to be missing something?)
Edit: Okay, sorry for the false alarm, guys. I rebooted my system and after that I was able to reach the config screen of each installed plugin and noticed that all settings are intact! So, problem