v4.21.2

Fixed

• Rubick starts on Ubuntu 22.04, Debian 12 and Linux Mint 21. The
  .deb, .rpm and AppImage needed glibc 2.39 and did not start there at
  all. They now need 2.35. (#319)

• The AppImage no longer opens a blank window on Fedora 44 and other
  distributions with a recent Mesa. It carried its own libwayland-client,
  and the page's process stopped with EGL_BAD_PARAMETER. (#319)