Photon Studio advertises free editing on macOS, including opening and saving layered PSD and PSB files, masks, adjustment layers and familiar Photoshop shortcuts. The developer also says editing and AI selection tools run locally without an account.
Those are unusually ambitious claims for a free application. The right response is a controlled test, not immediately moving a client archive: duplicate a small PSD with text, layers, masks and one smart object, open it, make a trivial change and compare the round-trip in Photoshop.
If the test succeeds, Photon could become a handy second editor on a Mac where a full Adobe workflow is overkill. If it breaks layer fidelity, it is still an interesting experiment and the original file remains untouched.