@arakiken I have built mlterm with Cocoa backend now, and apparently it still needs X11 to open settings window. Is this intended?
I would be nice to have native settings (though if it can only be done with fancy modern ObjC with clangisms, then X11 options should rather be retained, to avoid breaking the app on older macOS versions).
This is how it looks (image added for testing libsixel support):

Also, pretty much all expected macOS menus are absent. There is only one menu, mlterm, with two items in it (Config and Paste).
I have checked the build on Catalina (without my patches to fix build for 10.6), and it looks the same.