Installed ubuntu 18.04 dekstop. This picture flickers on the screen. What should I do? I tried to connect to different sources everywhere in the same way. Please help. Connect via ssh and everything works.

You need to capture your running log, before @numbqq or @Frank can understand the nature of the problem.

When you’re logged in via SSH, run the following commands:

Fetch system version information

khadas@Khadas:~$ cat /etc/fenix-release > ~/system-version.log

Fetch system kernel information

khadas@Khadas:~$ sudo dmesg > ~/kernel.log

Fetch system log information

khadas@Khadas:~$ sudo tar cvzf ~/systemlog.tgz /var/log/

Your Ubuntu OS will dump these logs into files, and you can use SSH to send them to a remote server or dump them into an SD card, then you can attach the links to download these files to this forum thread.