[bionsystem]

I use GTO+ which is proprietary.

I just tried this one which works like a charm (just run the exe from the zip in github releases ; even comes pre-loaded with a wide amount of preflop ranges, which seem to come from a previous solve) : https://github.com/bupticybee/TexasSolver

Searching with "poker solver haskell" only seem to show very immature projects.