A possible workaround found: looks like it might be indeed NVDA. The following suggested workaround is applicable for NVDA 2021.2 or older and/or if you are running alpha snapshots released earlier than August 12, 2021:
I will do my best to release an Add-on Updater update this weekend in hopes of resolving this situation - note that the update will be a manual one; if it works, I'll make it available to the rest of the community next week (even then, you must apply the update manually if you are impacted).