Don't want to start an off-topic discussion on Phabricator (phab:T212808) so let us continue this discussion here (link on your page in Phabricator led me here).
To be quite honest, between May 2017 and November 2018 I didn't have admin rights (click), so I cannot tell myself. But there's been this discussion on plwiki, which hints that the problem with our local gadget was caused by the OOUI change and hasn't been really fixed ever since. To clarify: I am not claiming that that OOUI change caused the TypeError I mention in phab ticket, just that our local gadget stopped working.
And I am not a fan of OOUI at all. Wherever I could, I have disabled any sorts of fancy looking "improvements", which, for me personally are downgrades. I have disabled this on RecentChanges, Watchlist and Search. I would disable it anywhere else as well, but I unfortunately cannot. There should be an option in Preferences to turn off OOUI look and just use plain html forms, as it was before. I am one of those veteran editors; I've been here (in and out admittedly) for 15 years (10 on this account) and I got used to the "old look". As one of plwiki's technicans I am not against changes so to say, I am against changes that are completely unnecessary. OOUI forms are taking more space on the screen than their plain html "counterparts". These widgets are also taking some time to load, which really pisses me off.
All I ask for is, give me the ability to choose. Best wishes for this New Year, tufor