

TrueNas is pretty top notch and offers a variety of storage and protocol options. If you’re at all familiar with Linux style OS, it should be pretty easy to work with. Setting up storage comes with a little bit of a learning curve, but it’s not too bad. This SAN/NAS OS is polished, performant, and extensible. If you’re not planning on using SMB or Samba, you can most certainly use NFS, or iSCSI if that’s your thing.
Have you tried using the steam mobile app? I think that has some advanced recovery options. Unsure if you can change the registered email that way, but might be worth a shot.
Edit: Specifically the Steam Guard feature.