Interesting, didn't know "iCloud Backup" could be self-hosted. I'm self-hosting everything else except for that one item on the list, I might as well make the jump.
The downside of self-hosting "iCloud Backup" is having to plug one's phone into one's computer every time they want to do a backup. There's probably a way to do a daily wifi sync using iTunes, but that doesn't seem to be documented anywhere.
I personally like how iCloud automatically backs up my iPhone whenever it's charging and connected to wifi.
Itunes can also sync over Wifi[1] or You can use Nextcloud[2]. You can backup your photos to your PC/Mac and then upload them to a cloud service. I use duplicati[3], it automatically encrypts and compress your files and uploads them to the cloud service of your choosing. I use Backblaze B2 for the cloud service($0.005/GB)[4].
[1]https://support.apple.com/en-us/HT210612
[2]https://nextcloud.com/install/#instructions-server
[3]https://github.com/duplicati/duplicati
[4]https://www.backblaze.com/b2/cloud-storage.html#why-b2-menu2