Hello!
I have updated my pgAdmin 4 from v4.27 to v4.28 and discovered that it won't start up in browser, because of MIME types of javascript files returned by server (maybe?).
I tried my best to fix this on my side, clearing all the caches in browser several times, rebooting the machine and reinstalling the software, but nothing helped.
According to the logs server started normally, but in browsers (Chrome and Mozilla) it doesn't work.
I'll try to roll back to 4.27 and use this version, hope this info helps to find and fix the issue:

Thanks for your great job maintaining this app!
Best wishes,
Sasha.