Then you copy the ssh public key from the phone to your "home-server", and setup a job scheduler to run rsync - now you have better than nextcloud syncing of your phones pictures/what-have-you with your home-server.
Setup of a ssh connection is similar to https, rsync exchange of rsync is usually "all good" and thats it. Rsync otherwise is a very efficient but not very documented protocol network-bandwidth-usage-wise.
Mesh? Syncthing, tried it, sucked for reasons I cant remember now. Nextcloud - had it for years, mind you I was contributed to nextcloud the android app, fixing many bugs, but still it caused me data loss / picture loss. Which I only found out after implementing the rsync solution and seeing OMG rsync found so many pictures Nextcloud was supposed to keep in sync for the past year but it just bugged over.