According to this ms office support article, OneDrive for Business has a limit of 400 chars, which is more than sufficient for Cryptomator.
260 chars is the limit for single path elements.
The FileSystemCapabilityChecker, that you apparently already met, is a bit too restrictive here. We will tell it to be more relaxed and just check for a 300 chars path length in tomorrows 1.5.1 release.
The maximum path length that can occur in Cryptomator is 268 chars (beginning from the d/ directory).