To add to this, virtually all GPUs out there with DP are DP++ and will not require an active adapter.
Consumers will almost never need to consider an active adapter for DP to HDMI, as well as single link DVI. HDMI to DP will always require an active (powered) adapter. As would DP to dual link DVI, VGA, or component.
Stand up a little VM with an install of Debian 9.
Don't mess with your main system, don't worry about flatpaks, and you can just get rid of it if you're done with it.