about:torconnect doesn't show when launching the browser in non-PBM

The only clue is:

JavaScript error: , line 0: TypeError: A promise cannot be resolved with itself.

And the UI for the page is disabled:

Screenshot

The workaround is to open a new tab, and about:torconnect will be shown there.

Even though say that officially we don't support non-PBM, this might be pretty bad for existing users and, more importantly, that message suggests that it might be a bigger problem.