@goemonsama Yo nice! I'm planning to move over myself once I can afford to build a new PC. Not exactly for W11 reasons, though that's a heavy consideration. I just want to challenge myself with a new OS and it's easier than ever to move.
Best of luck in your linux journey!
@wyatt It didn't need recapping. Perhaps it's still a good idea given its age, but it runs fine and none of the caps were leaking or bulging.
It's an ethernet C-bus board as you guessed, a Buffalo-branded one since those are ultra common and drivers are still hosted on their website.