3. Install the .deb packages.
In the subfolder of the extracted Blackmagic Desktop Video Linux folder, enter the following subfolder: deb/x86_64 (for 64bit systems, otherwise "deb/i386"):
If installing the packages throws the following error:
Setting up desktopvideo-gui (12.1a9) ...
dpkg: dependency problems prevent configuration of mediaexpress:
mediaexpress depends on libegl1-mesa (>= 7.8.1) | libegl1-x11; however:
Package libegl1-mesa is not installed.
Package libegl1-x11 is not installed.
... install "libegl1-mesa" manually before running "dpkg -i". The mentioned "libegl1-x11" seems to be an alternative option. On my system it was sufficient to install "-mesa". The "libegl1-x11" package wasn't even available/found on Xubuntu 20.04.3 (maybe different distro?)