I'd suggest to add an MSRV to the crate in the next release. And keep track of what bumps or not the MSRV. As basically anyone that has MSRV and builds on the top of this lib gets the CI crushed every time a new dependency is silently bumping the MSRV without you noticing (as you depend on things with "^0.x.x".
For more info, see: privacy-ethereum/halo2#207