[jonalmeida]

The developer had put out a note saying that Tab Groups won't be suppressed by WebExtensions, and the work in order to do a partial port isn't worth their time.

[nyordanov]

The developer of this alternative - https://github.com/denschub/firefox-tabgroups - has said that they will port the add-on to a WebExtension, but they are waiting on this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1384515