Can't type unicode character codes ending in 0 with hex input.
With the unicode hex input keyboard, I can type all unicode characters except if their code ends with a 0, in which case nothing happens if I try to type them out. So Option+03c1 outputs "ρ", but Option+03c0 (which should output "π") gives nothing at all.
(Probably related: https://discussions.apple.com/thread/253435504)
MacBook Pro 16″, macOS 12.1