i think a server would be overkill for most of these things, even the grocery list where youre sharing between multiple people. something like syncthing would be enough. its p2p so it just syncs over the network whenever both devices are available. for the grocery list theres definitely more chance that you could run into sync conflicts but you could grt around that easily by just having each person add items to a separate list then have the app show all items merged together into one list. basically something like todo.txt but with the ability to use multiple files