On Tue, Sep 10, 2019 at 12:06 AM Donn Cave
https://www.haskell.org/ghc/blog/20190825-ghc-8.8.1-released.html says
cabal-install users should note that cabal-install-3.0 or later is required for use with GHC 8.8.
I'm not the most sophisticated user of cabal-install ever, but it appears to me that 8.8.1 can't build 3.0.0.0? depends on base >= 4.8 && < 4.13, where 8.8.1 installs base-4.13.0.0.
lib:Cabal 3.0.0.0 can be build with GHC 8.8.1 as is evidenced by https://matrix.hackage.haskell.org/package/Cabal it's just the executable exe:cabal 3.0.0.0 that can't be build with GHC 8.8.1; It can however be built with GHC 7.10.3 through GHC 8.6.5 as evidenced by https://matrix.hackage.haskell.org/#/package/cabal-install However, exe:cabal 3.0.0.1 among other things is planned to be buildable also with GHC 8.8.1 But it's perfectly fine to use an exe:cabal built with a different GHC than the one you want to use it with; in fact exe:cabal supports being used with all GHCs going back to GHC 7.0 (even though you can't build exe:cabal with GHC 7.0 anymore)
I'm working with cabal-install-3.0.0.0.tar.gz . It looks like it might be possible to up some of the dependencies, like HTTP to 4000.3.14, but I suppose there's a reason why cabal-install itself isn't there yet.
Indeed, the main reason is that some of its dependencies weren't GHC-8.8.1-compatible yet at the time its release. So we didn't yet bother to update the bootstrap script yet. What operating system are you on? is it possible for you to use one of the binaries from http://downloads.haskell.org/~cabal/cabal-install-3.0.0.0/ in the meantime? Herbert