ansi-terminal-1.1, released on Hackage on 7 February 2024, now features in snapshot Stackage Nightly 2024-04-10. This version adds ‘fancy’ underlining, which might be fun to experiment with.
I anticipate that most packages’ existing use of ansi-terminal will be such that they can simply relax upper bounds on the dependency.
The new features are supported by all of: (a) Windows Terminal 1.19.10821.0 (in the Microsoft Store; the native terminal on Windows 11 and freely available for Windows 10), (b) current versions of popular (but not all) terminal software for Linux, and (c) current versions of popular (but not all) third-party terminal software for macOS.