It is not yet clear, when we can or want to drop GHC 8.10, but there is the intention to do this if possible and the following things currently depend on GHC 8.10 and thus need to be dealt with first:

• Last ghc version for which there exists the old ghcjs is 8.10 (maintainer: obsidian systems) haskell.compiler.ghcjs: remove at 8.10.7 #422342
• Some elm packages still need 8.10 (maintainer: @turboMaCk )
  • elmi-to-json elmPackages.elm-coverage: drop #415911
  • elm-instrument elmPackages.elm-instrument: build using GHC 9.4 #413234
• pakcs (maintainer: @t4ccer)
• yi (no maintainers)
• hasura-graphql-engine (maintainer: @Lassulus) (broken anyways)

GHC 8.10.7 (binary) is also used for bootstrapping other GHC versions:

• As boot compiler for GHC 9.0.2 haskell.compiler.ghc902: remove at 9.0.2 #381265
• As boot compiler for GHC 9.2.* (could be replaced by GHC 9.0.2)
• As boot compiler for GHC 9.4.* (could be replaced by GHC 9.0.2, but not 9.2.*) haskell.compiler.ghc902Binary: init at 9.0.2 #411397

That GHC 9.4 depends on 8.10.7 for bootstrapping is troublesome because:

• It is the latest GHC to support TemplateHaskell in pkgsStatic: Build failure: haskell.compiler.ghc{8107,902,92*,94*} on *-darwin #367686
• It is the latest GHC we can cross-compile which is interesting for bootstrapping a native GHC in the future (e.g. on riscv64-linux).