The version of GNOME Chess we ship is pretty old, version 3.34 has been released and is available in Debian. On top of that, the commits merged on GNOME Chess master directly on top of version 3.34 make it work for the Librem 5.
It would be nice to ship version 3.34 plus those extra commits, see https://gitlab.gnome.org/GNOME/gnome-chess/merge_requests/12 for more information. We would have to ship at least up to this commit from the master branch: https://gitlab.gnome.org/GNOME/gnome-chess/commit/2622a2e6c02bda295e9608354eab37a53e6cbd52.