I use a hetzner storage box with borg backups for my backups. It’s pretty cheap and has enough space for my VM and LXC backups, as well as my proxmox host backup. I don’t backup my media collection because that would cost a lot, and I can always redownload most of the things I have if needed.
The only thing I’d say is look into whatever tooling and scripts people have made for removing CSAM from your instance. I messed around with a Lemmy instance for a bit, but when I heard about how hard it was to deal with the pedos, I got a little scared about inadvertently hosting CSAM and decided to shut it down. Since then I think I remember hearing about some better automated tooling for that kind of thing though so hopefully you can set that up.
Look into Oracle cloud’s Always Free tier of cloud instances. I have a few of those and they’re decent for free.