Hi!

phodina 写道：
> Enabling support for X11 solves the problem.

Are you sure your Guix & mpv installation are up to date?

See

  https://issues.guix.gnu.org/59508 (patch)
  https://issues.guix.gnu.org/59279

and specifically

  https://issues.guix.gnu.org/59378#2 and linked
  https://issues.guix.gnu.org/59339

which mentions your exact error message as being fixed back in 
November.

Kind regards,

T G-R