I think all you can do about this is [complain to Apple][1] and use [Character Viewer][2] or the [ABC Extended][3] keyboard instead.

Making a custom layout for the characters you need most often with [Ukelele][4] may also make sense.  Or creating [text replacements][5] for them (for example using the hex codes as the triggers).

Update:  Still broken as of MacOS 12.6

Update:  Still broken as of MacOS 13.2

I think 256 codepoints are affected, but not all are occupied.  This chart shows them:

[![enter image description here][6]][6]


  [1]: http://www.apple.com/feedback
  [2]: https://support.apple.com/guide/mac-help/use-emoji-and-symbols-on-mac-mchlp1560/12.0/mac/12.0
  [3]: https://sites.psu.edu/symbolcodes/mac/codemacext/
  [4]: https://software.sil.org/ukelele/
  [5]: https://support.apple.com/guide/mac-help/replace-text-punctuation-documents-mac-mh35735/mac
  [6]: https://i.sstatic.net/4p0Qi.png