Lenovo think centre pcs are great home servers, I personally run debian on mine and have zero issues with it
Two things I can think of, it's either some remnant program from the original drive in which case just toss it or re-use it elsewhere and put your HDDs in, you don't know what the state of the OG HDD is anyway and for read/write heavy programs like plex or storage it's probably at a higher chance of failure
It has some kind of BIOS lock, you said you can get into the BIOS but have you tried to change anything? It might prompt you for a password In which case you might be able to reset the BIOS or will have to contact lenovo to sort it out if possible.
The worst BIOS password bypass Ive done is to actually fry the chip storing the password, there is so many things wrong with doing this but it MAY be possible as a last resort so please exhaust all other options before attempting this
I think this would be more effective on the fediverse too, bots are trying to engage as wide an audience as possible, which gives us a metric to monitor activity across the fediverse.
For example, a user might post an article to the news community on their preferred instances whereas a bot will unbiasedly post it on all instances it deems fit to share with.
This isn't perfect but it's another metric to help weight and quantify bot activity for an automated defense system. RSS feeds and the like can specifically flag their accounts as automated to avoid misbans from the system too