Despite this not being FOSS like GIMP, I think it's great that there is at least some very viable alternative that can run on Linux even with some workaround, for free (besides Photopea).
Glimpse was actually a good alt to Photoshop which actually was just a refined UI for Gimp under the hood. The project halted after their maintainers decided to stop it. Last I recall, they were definitely open source. IDK which license they used but folks could probably fork it and continue the work there as well.