All developers on my team (on macos) turned out to be running node14 in development mode even after upgrading to meteor 3 (meteor without fibers IS compatible with node14 so it doesn’t crash).
There seems to be some problem with the devbundle and installation.
You can check this easily using meteor node --version, it should NOT return 14.xxx
Solution if it does: rm -rf ~/.meteor and then reinstall meteor. It will also reclaim a lot of disk space 
Luckily you were running 14. Meteor comes a long way from Node 0.x … 
Meteor is like a Honda Civic. You run a version for 10 years then … you give it to a colleague, he changes the oil and runs it for another 10 years.
This sounds familiar to a problem I had pushing commits for a newly converted Meteor 3 app, which had Galaxy’s push to deploy set up.
I guess I have to find a way to nuke a build cache somewhere on Galaxy and it’ll solve it like in this case…?
(In the end it worked with a manual deploy, I haven’t returned to push to deploy yet while a few bugs linger in my current dev branch)