Vokoscreen 2.5 was removed in Trisquel 10

You have backports enabled, so backports updates will install.

You can downgrade by doing,

sudo apt install vokoscreen=2.5.0-4

As the 2.5 version is still on non-backports repositories.

Thank you, I see!

The "Software and Updates" of the system has been changed back to the previous settings.

Software & Updates -> Updates
- Subscribed to: Security and recommended updates

I selected "All updates" before.

Now the vokoscreen in the update source is 2.5.

Vokoscreen-ng is so hard to use! I recorded a video for 5 minutes, and the video file was damaged...

By Ark74:
sudo apt install vokoscreen=2.5.0-4

After using the above command to install, we also need to lock the Vokoscreen.

sudo echo vokoscreen hold | sudo dpkg --set-selections

Check whether locking is successful：
sudo dpkg --get-selections | grep hold

I suggest that the software source delete NG and keep only 2.5.