I installed gtk4 4.12.3+ds-1ubuntu0.1 from mantic-proposed on Ubuntu 23.10 and verified:
Test Case 0: The autopkgtests and build tests have all passed.
Test Case 1: Opening and saving files from the Firefox and Chromium snaps still work.
Test Case 2: The portal-test app seems to work about as well as before.
Test Case 3: gtk4-demo, nautilus, and gnome-text-editor continue to launch and work as expected.
I installed gtk4 4.12.3+ ds-1ubuntu0. 1 from mantic-proposed on Ubuntu 23.10 and verified:
Test Case 0: The autopkgtests and build tests have all passed.
Test Case 1: Opening and saving files from the Firefox and Chromium snaps still work.
Test Case 2: The portal-test app seems to work about as well as before.
Test Case 3: gtk4-demo, nautilus, and gnome-text-editor continue to launch and work as expected.