This isn't specific to Edge Chromium as most other Chromium-based browsers have this same issue, but it's one that prevents me from switching to any other browser.
This extension, Join by joaoapps, is one I heavily rely on to mirror my phone's notifications to my PC, sync my clipboard across devices and send SMS from my PC (I know Pushbullet is a good alternative that would probably work but the subscription model is too expensive).
Most other Chromium browsers are missing certain components Chrome has, which causes this extension to not work, and Edge seems to be the same, but I'm not sure what's actually missing (I'm no good with the developer side of things).
Is anyone able to offer any insight as to whether Edge Chromium may eventually support this extension? Thanks in advance! :)
That is an interesting discovery. We are still in earlier builds and I am sure that as the development proceeds, more extensions will become compatible. I will bring this one to the attention of the product team.