Might cause some spam after every new version, not sure how that community would accept it.
There are more than 20 instances than have more than 300 monthly active users (https://fedidb.org/software/lemmy/), if all of them announce their updates there,, that could be quite a lot.
I would suggest people who are really invested in a community to follow that community's instance meta/main community
Probably needs a new comment to get people to converge indeed