EpiphanyDevel disables the shader cache because it thinks the folder doesn't exist
With the EpiphanyDevel flatpak from gnome nightly, this gets printed multiple times in the terminal on startup:
Failed to create /home/user/.var/app/org.gnome.Epiphany.Devel/cache for shader cache (No such file or directory)---disabling.
...even with the local storage/caching setting turned on in the Privacy tab in the Preferences dialog. And yet, the folder exists, and has subfolders:
$ ls ~/.var/app/org.gnome.Epiphany.Devel/cache
epiphany
fontconfig
mesa_shader_cache
tmp
webkitgtk-6.0