> The most obvious solution would be make a small PC: more powerful and bigger fans means less noise

In the performance window of "old Thinkpad", why not go fanless? Those lovely little Intel N150 mini-pc boxes are mostly fanless and completely silent - I have on my desk running Jellyfin/web server/etc, and it's inaudible under load.

> but what if it fails to start?

In ~15 years of running headless linux boxes, I've never had one crippled to the point it wouldn't boot as far as ssh.