Possibly related to Bug 1174534?  Igor, it might be helpful if you could try downgrading sddm to see if that helps.  There's a version at <https://build.opensuse.org/package/show/home:psych0naut:branches:KDE:Frameworks5/sddm> that you can build yourself locally.  (And maybe eventually the CI system will publish binary packages; they're not there yet.)

Can't download, because have no login to build.opensuse.org. It did not permit download without login. Try to find this old build and find it on leap 15.2 (0.18.0-lp152.4.11)
After installing this version all works fine. So perhaps this bug is related to Bug 1174534 (https://bugzilla.opensuse.org/show_bug.cgi?id=1174534)

Possible(In reply to Igor Kuznetsov from comment #2)
> So perhaps this bug is related
> to Bug 1174534 (https://bugzilla.opensuse.org/show_bug.cgi?id=1174534)

Definitely possible. How is x2go (more specifically, the component which connects to X) launched? Is $XAUTHORITY set?

(In reply to Fabian Vogt from comment #3)
> Possible(In reply to Igor Kuznetsov from comment #2)
> > So perhaps this bug is related
> > to Bug 1174534 (https://bugzilla.opensuse.org/show_bug.cgi?id=1174534)
> 
> Definitely possible. How is x2go (more specifically, the component which
> connects to X) launched? Is $XAUTHORITY set?

Very similar. And it stop worked after big update, where sddm was updated to new version. now sddm version is 0.19.0-1.1

if run echo $XAUTHORITY on local console so output is done (/run/user/1000/xauth_hZMsB), but if connect via ssh to remote pc, output of echo $XAUTHORITY is empty.

so bug stil persist.

x2go still did not work.. very sad

after similar updates it is work fine, but only after creating file /etc/SuSE-release on server

after similar updates it is work fine, but only after creating file /etc/SuSE-release on server

*** Bug 1074241 has been marked as a duplicate of this bug. ***