This is fixed in emersion/xdg-desktop-portal-wlr#191, however xdg-desktop-portal-wlr has not had a release since.
Even if I use xdpwlr directly from git, it might not actually work, and I'd need a patch for wlroots. It might work for the things I care about, though, considering the Hyprland portal worked fine, so I should try that.
Since #299 I'm using sway, which uses a different xdg-desktop-portal implementation than Hyprland.
Apparently, nvidia produces images in an unsupported color format, which causes xdg-desktop-portal-wlr to crash.
This is fixed in emersion/xdg-desktop-portal-wlr#191, however xdg-desktop-portal-wlr has not had a release since.
Even if I use xdpwlr directly from git, it might not actually work, and I'd need a patch for wlroots. It might work for the things I care about, though, considering the Hyprland portal worked fine, so I should try that.