error in loading a lyx document in a newly installed lyx 2.4.0 -alpha3

[Wolfgang Engelmann]

Am 13.02.22 um 19:31 schrieb Wolfgang Engelmann via lyx-users:
> This I get in trying to load a lyx file:
> 
> /tmp/lyx_tmpdir.hJBMjulqOCPq/Buffer_convertLyXFormatBepJfy.lyx ist kein 
> lesbares LyX-Dokument.
> 
> The same happens if I remove the tmpdir and try again
> 
> Wolfgang

additional info.

I start the lyx 2.4.0 -alpha3 from
$ lyx &
[1] 5015

I get
wolfgang at Fuji:~$ qt.qpa.xcb: QXcbConnection: XCB error: 5 (BadAtom), 
sequence: 598, resource id: 0, major code: 20 (GetProperty), minor code: 0

and lyx opens


I open Jürgens chapter01.lyx which is displayed ok
Same with his master
and the example books/American_Mathematical_Society_AMS

If I open a document of mine, it says:

/tmp/lyx_tmpdir.ADxVERtFAZnB/Buffer_convertLyXFormatbyAYvt.lyx ist kein 
lesbares LyX-Dokument.

If I go to to this lyx file
/tmp/lyx_tmpdir.ADxVERtFAZnB/Buffer_convertLyXFormatbyAYvt.lyx

I can open it with lyx but it is empty

How should I try to find out whats going oß

Wolfgang