This was a challenge. I ended up with a small powershell script setting the http and https url associations to ChromeHTML. Clicking a link in Outlook opens a window to set the default browser, where I could choose Google Chrome and his seems to hold.
I understand Microsoft thinks about giving up on browser development since they lost the browser war. Why still push Edge? Edge on Android was too early. First fix bookmark manager etc. Do it for your users, not for profits, ....