There is the MangaDex@Home, where users can serve part of disk space/bandwidth to help serve (mainly old) manga chapters. It does need to be something that is running 24/7 (e.g.: not a PC that is shutdown frequently), so something like a VPS or a service is recommended.
Virtually every chapter is served via MD@H now.
Client doesn't really need much availability, as long as it can do a graceful shutdown. Even in the event of a sudden shutdown, the trust penalties are much lower than H@H and in practice go away after a trickle of traffic to raise your score
Nice, didn't know about this (there isn't much information about MD@H after the rewrite).
BTW, how can I register my VPS on MD@H? Before we had a dedicated form on the page to register interest, at least after the rewrite I didn't find it. Is it only using something like Discord?