This sounds more like a network problem, maybe something on your end or that one of the repos was temporarily unreachable (usually it's the postmarketOS repo for me in such situations). I recommend running sudo apk update in situations like this and reading through the output. Depending on which repo is unreachable (= if it's one of the alpine repos) it may be a better idea to delay upgrading.
It definitely has nothing to do with the device being dropped from main to community โ both categories mean that the device is served by stable.
Hope this helps!