We gave up on Rspack and went back to the Babel bundler. At least we’ll still get the bug fixes and Node updates on new versions. And we did quite a few changes to make it work. That work will be there when the team gets the bugs fixed.
I really hope this new way of releasing marquee features, then moving on to the next big thing before the prior big thing was fully baked, isn’t the new standard of development for Meteor. There sure are a lot of Modern Build bugs open on Github. 