I can't get houdini 16.5 to display large enough so I can at least read the text and see the icons. I did lot of searching/reading and trying solutions from online posts and nothing has worked. Tried MS win 10 scaling, registry edit, and houdini.exe-properties-compatibilty settings and nothing works. How can I get houdini to display large enough to read on my 4k display?

If you can manage to use the system magnifier for a few seconds:

0) Open Houdini.
1) Edit > Preferences > General User Interface.
2) Set Global UI Size to High DPI.
3) Click Accept.
4) Close Houdini and reopen it.

Hopefully that works.

You can apparently also start Houdini from the command line as houdini -highdpi