setting frame size with C-5 2 - emacs 30.5

[H . -J . Heitländer]

Hi there,

since several months the behavior of C-5 2 has changed (for me).

Somehow the new frame only is 16 char wide and 6 lines high. (text window).

Additionally the variables "frame-char-width" resp. "frame-char-height" 
don't seem to be defined.

I'm on "debian testing" with wayland (xwayland) as the display 
protocol(?) Is there a way to set the size of a new frame generated by 
C-5 2?

Searching the docs/internet did not give any result so any help is welcome.

TX in advance

Heiner