Maybe try Stash, it has gallery support too https://github.com/stashapp/stash

Also, what about jellyfin itself? It also supports photos

Lots of malware gets hosted using dynamic DNS domains, so they (or more likely some bot) probably saw the domain frequently showing up in malicious activity and blocked it without understanding that it itself isn’t the source of the malicious activity.

You can use cryptsetup-reencrypt to encrypt an existing disk in place with LUKS. Then you just have to modify the initramfs/bootloader/fstab to point to the new configuration. See https://wiki.archlinux.org/title/Dm-crypt/Device_encryption#Encrypt_an_existing_unencrypted_file_system