May 26 '22 UPDATE: On the plus side: my PC doesn't freeze anymore. So, the extremely bad outcome from the March update has been changed back to just an unusable state again, like it was before that update. Same procedure as last time: was jubilant at the prospect of an update - applied it, it worked for about 3 hours (yay!), then the dreaded conflict with Google docs + mail appeared again: they go offline and keep trying to reconnect. Who knows why. (Really: who knows??) I have to use G for work; it's sadly not a choice, as I despise the company and its products. Oh irony: this add-on works together perfectly with GDocs + GMail in a Chromium browser.

UPDATE: My hopes that the recent, March '22, update would fix things have sadly turned out to be utterly wrong. It has gotten worse. I reproduced it now **4** times, all with the same outcome: now, instead of only Google docs getting extreeeeemmmly slow and constantly dis- + re-connecting my system absolutely freezes. As in nothing works anymore, I can't even get to Alt+F2 xkill and have to push my PC's reboot button.
On the plus side: as soon as I turn the add-on off again, it feels like I have a super-speedy, new PC!

When it works, it's great! I need it for work, but sadly, updates during the past year started to conflict with Google Docs. For my work, I need to have several google docs open at the same time -- and whenever this add-on is enabled, those are in a constant "(trying to) re-connect" loop. And my CPU usage is through the roof (showing that an add-on is using significant resources, not a webpage, so for once it's not Google's fault. For the record: I hate Google docs with it's insatiable hunger for RAM!) I only realized after extensive trial and error that it's this add-on's fault. As soon as I turn it off, everything works fine again. Every update gives me hope, only to be squashed again after a few minutes of working fine.
I'm on latest Firefox ESR, Linux Mint 19.3.