Looks like this package broke after a deprecation in Nim 0.20.0. See [https://github.com/nim-lang/Nim/blob/devel/changelogs/changelog_0_20_0.md#breaking-changes-in-the-standard-library](https://github.com/nim-lang/Nim/blob/devel/changelogs/changelog_0_20_0.md#breaking-changes-in-the-standard-library).
_case object branch transitions via system.reset are deprecated. Compile your code with -d:nimOldCaseObjects for a transition period._ So the best short term "fix" would be to clone that repo, and build it locally using nim c -d:nimOldCaseObjects ...
