I cannot find this statement in the release notes. The only reference to cabal versions is in the 2.1.11 section talking about the package database coming with the release.
Despite of the warning, cabal 3.10.1.0 does seem to work with ghc 9.8.1.
Additionally, if cabal-install is rebuilt with ghc 9.8.1 as below:
cabal install cabal-install --allow-newer
even the warning disappear and the new cabal seems to work fine, at least for me so far. This build uses sources from Hackage only.
Edit: I sent my reply above by email two days ago but it never landed here for some reason.