I think that the problem exists because the Microsoft deb file puts the key into etc/apt/keyrings (deprecated) rather than into usr/share/keyrings (current standard). The user gets a warning when sudo apt update is run: “Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.”
If you still have your 20.04 build available with Edge installed, run sudo apt update and I suspect you’ll see the warning if you installed Edge opening the deb file rather than installing through the terminal.
At present,having the key in etc/apt/keyrings doesn’t affect functionality (it is just a warning), but in time it will. Microsoft needs to rebuild the deb file so that the key is signed and installed in usr/share/keyrings. Meanwhile, it isn’t all that hard to fix using the terminal.
As a side note, terminal installation instructions available in the Ubuntu forums can be used to set up the keys correctly as part of the installation process. This one is on Microsoft.
Update/Edit 4/3/2022:
I installed Chromium, Brave and Vivaldi from the “Browser Ballot” this morning to see what would happen. Vivaldi (deb) created the deprecated key location problem. Brave (deb) and Chromium (snap) did not.
This is not a UB 22.04 issue, although Debian/Ubuntu made the decision several years ago to deprecate the old etc/apt/keyrings standard and replace the old standard with a newer, more secure, standard. It is a vendor issue. Vendors (and the issue affects many apps, I’ve learned) will eventually solve the problem by locating the key in the right place. Until then, the issue will continue.
Update/Edit #2 4/3/2022:
I dug a little further. Debian 11 and Ubuntu 22.04 LTS support etc/apt/keyrings, although those will be the last Debian/Ubuntu releases to do so. The issue is not, accordingly, critical at this point, although sudo apt update will warn about each key stored in etc/apt/keyrings. Beginning next fall, however, Ubuntu and Ubuntu-based distos 22.10 and subsequent will no longer support the old standard and the issue will come to a head.