Hmm, maybe looking at btop memory usage is too naive.

I'm not very knowledgeable here, but apparently that includes the memory of libraries that other gtk4 apps would share.

If I launch 5x instances of my app and look at /proc/<pid>/smaps:

    | PID    | Private | PSS      |
    |--------|---------|----------|
    | 360955 | 65.4 MB | 133.0 MB |
    | 360956 | 52.1 MB | 105.0 MB |
    | 404303 | 65.8 MB | 132.9 MB |
    | 404304 | 65.8 MB | 133.2 MB |
    | 404305 | 65.9 MB | 132.6 MB |

Looks like PSS includes private memory + shared libraries divided by the processes using them, so a little better than the 200mb that btop shows, but still over 2x heavier than, say, a hello world on macOS.