If I had to guess that’s gonna be a quirk of ActivityPub, and should self-resolve in a little bit, but I’m not an expert so don’t take me at my word there. I have some experience self-hosting setting up my own homelab over the last 2-3 years - if you’d like some “getting started” conversation, feel free to send me a DM or contact me on Matrix @darohan:tchncs.de
BTW modern KDE still has this as a module and it works pretty well with both Qt and GTK programs (though with GTK it sometimes shows it in both locations).