gThumb is barely recognisable in its GTK4/libadwaita port

gThumb 4.0 alpha has been rewritten in Vala and ported to GTK4/libadwaita, resulting in a significantly redesigned UI. The update brings better spacing, clearer hierarchy, and new features including WEBP/PNG animation support, JXL export, and a censor filter. Some existing features like web albums, contact sheets, and the find-duplicates tool were dropped in this alpha. The app remains a viable alternative to cloud photo services for privacy-conscious users or DSLR shooters.