On 18/02/2021 14:05, Eli Zaretskii wrote:

[sorry for the delay]

> Please try "emacs -q" (lower-case "q", not "Q").  If the problem
> happens with -q as well, then its cause is somewhere in all those
> site-start.d/50*.el files Emacs loads at startup -- those come from
> your system's Emacs distro.

The problem still occurs (see screenshot).

(No idea why all applications open full-screen on all new Linux distros)

> If the problem doesn't happen with -q, then its cause is in your init
> file, ~/.emacs.

As I said in the report, this is not possible: the error occurs still 
when .emacs is deleted.

Peter