Cygwin: ssh and ssh-keygen do not react at all

I've got a strange behaviour of ssh and ssh-keygen: they do not react at all. Cygwin is started with admin rights and works normally. The host 192.168.1.1 is up and I can remote desktop to it:

When I try:

$ ssh -vvv pi@192.168.1.1
OpenSSH_8.3p1, OpenSSL 1.1.1f  31 Mar 2020

I get only one line but nothing else, even if I wait hours. I reinstalled cygwin, openssh, I deleted the .ssh folders, no success.

When I enter

ssh-keygen -b 4096

nothing happens at all. For me it seems that the user interaction does not work. Any ideas?

Thanks

Update: I tried:

1. reinstalling cygin for all users, one user, running the installation with admin rights, without. No success.
2. Started ssh and ssh-keygen with an absolute path to make sure that the windows openssh is not used
3. Checked the folder permissions on .ssh

Here is my strace: Pastebin

Update 2: I found the following: if I run ssh-keygen or ssh often enough (!) it will sometimes work! Now that's weird.

I found that it is down to a bug in epclient64.dll of citrix: it crashes my ssh in my internal network. After uninstallation of citrix it would work normally. Here is the log

Pastebin log of strace
https://pastebin.com/FJfUj3C1[Pastebin][1]

Without the app protection it works fine. So to sum up:

• with app protection ssh crashes again and again, it does not even start properly
• without citrix ssh works fine
• citrix without app protection ssh works fine

--> epclient64.dll does not work with ssh

And we are talking about the most recent versions of ssh & citrix as of Jan 2021.