I recently upgraded to 20H2 had had the usual list of issues but sorted ok.
Two days and two reboots later Outlook stopped following hyperlinks
Went through all the advice on Google, everything was ok.
Found an article on Microsoft site.
Two machines, one with unconfigured Outlook had all the necessary registry entries, machine I use did not.
Exported the missing keys from one machine and imported into the other.
Reg import reported success but had not worked - strange, have done this many times over the years.
Put the keys in manually and Outlook now works ok..
These are the instructions

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\htafile\Shell\
Add missing keys -
\Open\Command\
"default" - created automatically
Then put a value into the "default" of the Command key
C:\\Windows\\SysWOW64\\mshta.exe "%1" {1E460BD7-F1C3-4B2E-88BF-4E770A288AF5}%U{1E460BD7-F1C3-4B2E-88BF-4E770A288AF5} %*

Thats it.