Not really an issue at the moment, since have fixed it here, and, yes, I didn't follow the recent threads on issues with making use of waterfox/firefox, but, just did a completely clean reinstallation of my windows 10 64 bit machine from scratch, and, while installing software packages, and reconfiguring combinations of NVDA and add-ons, etc., I found out that the moment I installed global commands extension, both waterfox and firefox no longer seemed to allow me to interact with the web-page contents, besides tabbing through all elements.
Chrome-based browsers, like chrome itself and brave still seemed
to work fine, though.
When I then went into the global commands extension settings, and, turned off it's extended virtual buffer extension, suddenly both those browsers, running versions of the same engine under the hood started working fine again.
In other words, just posting this here in case it's affecting someone else, and, in case this form of a solution wasn't figured out in the prior thread - sorry if duplicate info.
"...resistance is futile...but, acceptance is versatile..."