I can't even think of a single example. Most filesystems just offer 255 8-bit units to filenames, where 4-byte UTF-8 sequences are totally a non-issue. ZFS supports utf8only=on, which enforces that filenames do conform to UTF-8, in which case... 4-byte sequences are still not a problem.
What's the filesystem that doesn't allow it?
> their implicit normalization rules can trip up programs which expect behavior closer to POSIX norms
Most of them don't concern over character encoding and UTF-8 sequences are just as-is. ZFS is again the special case, the normalization property will normalize names on lookup (they are stored as-is).
A reasonable person[1] might argue that this is too liberal. IMO the exclusion list should be larger, but silently and automatically rewriting an application's filename into something else at creation time is too far.
[1]: https://dwheeler.com/essays/fixing-unix-linux-filenames.html