There is no FPC + Lazarus releases which works well...
For Linux, I can say only from my experience. I have installed Kubuntu 24.10 while ago and it come only with Wayland, there is no way to switch to X11 anymore, unless install xorg additionally, then you can switch to X11 during login. And under Wayland, there is no way that IDE works correctly, nor applications made with Lazarus. Lazarus and FPC are locked to X11 and GTK2 for now. I think GTK3 was and still is not finished (I can't see roadmap due some AI nonsense limitation).
Probably there is no way that GTK3 widgetset ever be finished nor full Wayland support. Thus also applications are locked to GTK2 as well. I do not know for Qt5, Željan Rikalo (zeljko here) can say more as he is the only person who worked on it, IIRC.