For documentation please see
https://cabal.readthedocs.io/en/3.8
for API documentation and changelogs please see
https://hackage.haskell.org/package/Cabal-3.8.1.0
https://hackage.haskell.org/package/Cabal-syntax-3.8.1.0
https://hackage.haskell.org/package/cabal-install-3.8.1.0
https://hackage.haskell.org/package/cabal-install-solver-3.8.1.0
and for binaries, please use ghcup or download from
https://downloads.haskell.org/~cabal/cabal-install-3.8.1.0/
Some release highlights are on these threads:
https://twitter.com/jneira/status/1557477176102031360
https://discourse.haskell.org/t/just-released-cabal-3-8-1-0/4920
https://www.reddit.com/r/haskell/comments/wm656h/just_released_cabal_3810/
The currently known and not yet fixed regressions on 3.8 branch compared to cabal 3.6 are listed at
https://github.com/haskell/cabal/labels/regression%20in%203.8
and the fixed regressions (but you need a newer version, once it's released, to benefit from the fixes) are at
https://github.com/haskell/cabal/issues?q=label%3A%22regression+in+3.8%22+is%3Aclosed