If I’m using Linux on a VM, it’s Debian (currently the testing branch) with XFCE (X11). Lazarus works well on this setup - I’ve been using GTK3 for a few weeks now, and GTK2 before that. I always work with the Lazarus trunk version (always up to date) + FPC 3.2-fixes (also up to date).
I installed an additional DE on this distribution to see what Lazarus GTK3 looks like.
And unfortunately, when using a non-docked IDE in Wayland, you have to disable the “Automatically adjust IDE main window height” option and get annoyed that the windows reset to the center every time you launch them - although with Cinnamon Wayland (currently an experimental version), there is hope that it will work properly in the future - windows position themselves from the top-left corner of the screen, and the position of the main window (with the menu and component palette) is remembered.
For a docked window, it works well on every DE, whether in X11 or Wayland.
During testing, I performed several basic operations in the IDE (dropping components onto a form, resizing components, automatically generating events, and entering simple code into them).
Screenshots:
https://brudnopis.ovh/lazarus_gtk3/