Is there a limit on how often you can request analysis? I like to run computer analysis after my games, but not sure if there's a limit (e.g. 20 times per day or something).
Yea. IIRC it's currently set to 30 per user per day to avoid abuse.
According to this:
lichess.org/features it is indeed 30. But if you become a patron, you can increase that number to 30.
What exactly is abuse for requesting computer analysis (I'm dumb)?
The analysis is done server-side. Uploading hundreds of games and requesting analysis for each one would drain a lot of server resources.