This is not a communication problem. Communities are indeed centralized and if an instance is shut down permanently or loses its data all the communities are gone. This is a big design problem of Lemmy.
Edit: it's sometimes possible to rebuild new communities on another instance and recover past messages that have been replicated on other instances (if there were full replicas) but this requires all users and moderators to agree on where to migrate and avoid splits and so on.
Terminating a support contract, in itself, is not a GPL violation. The restrictions only affects the ability to receive future updates.
Edit: Red Hat indeed claims that no GPL violation is happening, yet they inform their customers that sharing updates leads to contract termination, which clearly breaches the GPL at least in spirit: https://sfconservancy.org/blog/2023/jun/23/rhel-gpl-analysis/