You don't need the cloud: syncthing can sync your phone and your computer together without any issues. No nasty cloud provider involved: https://syncthing.net/
Also, you can restore an iPhone from what SyncThing can back up. Only an iTunes or equivalent iCloud device backup can. They also can’t back up things like MFA keys / seeds / IVs.
I’m glad ST exists and it’s useful for syncing photos for home use, but it is not a viable iCloud alternative, nor could one be made due to the private iOS API issue.