Samsung DEX layout switching conflict

I'm using swiftkey with my Galaxy S9 and recently started using DEX functionality - it's a Desktop EXperience from samsung, provides desktop layout with connected external display and keyboard/mouse. I'm using 2 languages: english and russian, and while the Swiftkey is active I can not switch languages neither with native Ctrl+Shift shortcut nor with samsungs shift+space, although I checked that in Swiftkey settings dual language is enabled for physical keyboard and there's a shortcut to switch between them.

As long as I switch to the native samsung keybord everything is ok, but it's pretty inconvenient to switch the keyboard before and after connecting external display