The solutions were executed with GHC 9.0.2, so that's what you should get with ghcup.
To run them, switch into the corresponding day* directory and run them Main.hs:
For the first two days, use
cd day1
runhaskell Main.hs
From the third day on, use
cd day3
cabal run
The original-attempts branch contains my original solutions.
The main branch can contain updates to my solutions inspired by others I found later, and also translations of alternate solutions to compare and study.