I think if I’m following all of the breadcrumbs correctly, a fix is in the works!
The issue was first reported here:
Allow or not accented characters in category slug according to "slug generation method" setting
Then it looks like @Falco started working on a fix at the end of this duplicate topic:
Category slug containing Unicode characters results in redirect loop
That was then superseded by this pending PR:
https://github.com/discourse/discourse/pull/11277
So it should be fixed soon from what I can tell.