WebKitGTK has a MiniBrowser that works nicely to have 2004Scape standalone, and it supports native Wayland!
Works Live too:
On openSUSE MiniBrowser is provided by webkit2gtk4-minibrowser package (there’s gtk3/etc versions)
I launch with:
'/usr/libexec/libwebkitgtk-6_0-0/MiniBrowser' --autoplay-policy 'allow' --private --features='-PreferPageRenderingUpdatesNear60FPS' 'http://localhost:8888/rs2.cgi'
I’m not sure if PreferPageRenderingUpdatesNear60FPS is needed (I still get 70+ on vsynctester), but apparently there was a thing on iOS with iPhones and 120Hz screens where Safari would lock to 60Hz unless that setting was disabled.