This is also occuring on linux. A friend told me to try signing out of my Microsoft account in the launcher and signing back in, but now I cannot sign back in. The sign-in page always comes up in a seperate window with "Failed to load the page. Please check your internet connection and try again. Error message: ERR_NAME_NOT_RESOLVED (code=-105)."
I've checked my hosts file and my firewall rules, as well as my router settings. There shouldn't be anything preventing my computer from accessing Microsoft's authentication services. I'm at a loss at this point.
Edit: after getting frustrated with actual troubleshooting, i started just clicking things in the launcher. After clicking some link that opened my web browser and took me to my XBox Live account, i went back to the launcher and tried logging in again and it finally just worked. Not sure why, but it did. I feel compelled to point out that I was able to log into my Microsoft account in my browser this whole time, and that if Minecraft opened the default/system browser and used that for authentication, you know, like most apps do, it would've worked fine. Instead, they've got some janky setup that opens a chromium window with no address bar or controls for troubleshooting and uses that for auth. And for some reason, that wasn't able to connect to their site... while I was able to connect just fine in Firefox. Good grief.
This is definitely a valid issue, it happens repeatedly and requires a change to your product in order for it to stop occuring. That would constitute an issue for a bug tracker, right?