Steam/flatpak on Funtoo: libGL error

I have used flatpak to run Steam on Funtoo (Gentoo derivative, 64-bit only) for some time now. Recently, it stopped working. The Steam window appears, checks for updates and installs them if found, then crashes.

When run from a terminal as opposed from the GUI icon, it reveals this error:
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast

I have a nvidia card, and use the nvidia binary drivers, currently version 450.57. I also have mesa installed, and checked if there’s any library conflict but it doesn’t appear so:
sudo ldconfig -p | grep -i gl.so
libwayland-egl.so.1 (libc6,x86-64) => /usr/lib/libwayland-egl.so.1
libwayland-egl.so (libc6,x86-64) => /usr/lib/libwayland-egl.so
libobs-opengl.so.0 (libc6,x86-64) => /usr/lib/libobs-opengl.so.0
libobs-opengl.so (libc6,x86-64) => /usr/lib/libobs-opengl.so
libmypaint-gegl.so.0 (libc6,x86-64) => /usr/lib/libmypaint-gegl.so.0
libmypaint-gegl.so (libc6,x86-64) => /usr/lib/libmypaint-gegl.so
libftgl.so.2 (libc6,x86-64) => /usr/lib/libftgl.so.2
libftgl.so (libc6,x86-64) => /usr/lib/libftgl.so
libfltk_gl.so.1.3 (libc6,x86-64) => /usr/lib64/fltk/libfltk_gl.so.1.3
libfltk_gl.so (libc6,x86-64) => /usr/lib64/fltk/libfltk_gl.so
libTKOpenGl.so.11 (libc6,x86-64) => /usr/lib/libTKOpenGl.so.11
libTKOpenGl.so (libc6,x86-64) => /usr/lib/libTKOpenGl.so
libQt5OpenGL.so.5 (libc6,x86-64) => /usr/lib/libQt5OpenGL.so.5
libQt5OpenGL.so (libc6,x86-64) => /usr/lib/libQt5OpenGL.so
libOpenGL.so.0 (libc6,x86-64) => /usr/lib/libOpenGL.so.0
libOpenGL.so (libc6,x86-64) => /usr/lib/libOpenGL.so
libGL.so.1 (libc6,x86-64) => /usr/lib/libGL.so.1
libGL.so (libc6,x86-64) => /usr/lib/libGL.so
libEGL.so.1 (libc6,x86-64) => /usr/lib/libEGL.so.1
libEGL.so (libc6,x86-64) => /usr/lib/libEGL.so

I also tried removing the flatpak Steam installation and reinstalling from scratch, but the same error happens. I would really appreciate any help with this.