This was one of my last de-googling projects, I currently self hosting photoprism, I have syncthing that syncs my photos to a network attached storage....at 3am it copies those pictures to a permanent location (I do 3am because during the day if you want to delete any photos etc. Before it syncs with photoprism.... At 4am my nas backs up to another nas (they are just a few portable HD for redundancy) photoprism works great for me, not as powerful as say Google photos, but close 2nd for me..... And for accessing the photos when not at home, have setup wireguard VPN for away from home access....... I see you want automatic deletion of the photos on your phone, I'd say you be able to run a CRON job that maybe every day (if you have made sure that your pictures are for sure being backed up in the middle of the night, that would automatically delete your dcim pictures folder..... I also run graphene, I'll give it a try and let you know if it works

P.s. my NAS drives are connected to a raspberry pi