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Someone has been working on an installer for Gimp 2.10 (stable branch): https://gitlab.gnome.org/GNOME/gimp/-/issues/9170#note_1687944. Same work will be done for main branch.
This experimental installer is now available here: https://www.gimp.org/news/2023/08/13/experimental-windows-arm-installer/ .
Continuous Integration
GIMP foundation runs its own farm for CI. A community member has offered to use his person WoA machine for the purpose, more is being provided for their use by Arm.