For anyone who did not think about it beforehand and struggled as me. You can run KDE Connect on your machine and send keyboard and mouse inputs using kde connect. Almost 0 input lag. So you can do all you need.

For me it was terminal and some work with files on dolphin (for emudeck). I’m not used to steam deck touch pads yet and using shortcuts on keyboard made everything a breeze.

You can transfer files, too, of course.