Is there a setting I need to enable to allow me to use multiplayer through Eclipse?  Launching the client works, but the multiplayer and realms button are greyed out and hovering over them gives me a "multiplayer is disabled" tooltip that asks me to check my Microsoft account settings, which is... not great for testing purposes.  I know on the server end you have to put it in offline mode to be able to sign in, but I've never seen it have this happen on the client end.

Update: After much more digging, I finally found an answer: Microsoft must've changed something on their end that altered authentication.  If multiplayer is showing as disabled for you, you need to follow the steps listed here to get your access token from a profile that authenticates normally outside the dev environment:

https://gist.github.com/50ap5ud5/beebcf056cbdd3c922cc8993689428f4#minecraft-authentication-in-dev-environments

In my case it turned out I just needed my access token, it may or may not still need the UUID.  The guide is older so I don't know how many versions it will hold up in, but in my case this did seem to be what Eclipse was looking for.