On a hunch I opened Gnome Software with flatpak and snap support. It turns out OpenShot is available via flatpak, so I installed it, and got the latest version 3.0, which seems to run...
HOWEVER I could not open my old projects from older versions of OpenShot.
I tried a few different things with varying success, but this isn't a bug report about OpenShot 3.0, so here's how I was able to run OpenShot 2.6.1 and open my old OpenShot projects:
1) Install the last commit of 2.6.1 (from 2021-11-13)
I too was unable to run OpenShot on Ubuntu 20.04.
On a hunch I opened Gnome Software with flatpak and snap support. It turns out OpenShot is available via flatpak, so I installed it, and got the latest version 3.0, which seems to run...
HOWEVER I could not open my old projects from older versions of OpenShot.
I tried a few different things with varying success, but this isn't a bug report about OpenShot 3.0, so here's how I was able to run OpenShot 2.6.1 and open my old OpenShot projects:
1) Install the last commit of 2.6.1 (from 2021-11-13)
$ sudo flatpak update --commit= 655abaeb016337c ca867fb0ddeee99 854e624b0e1c193 5bfeba60609dc9c 912f org.openshot. OpenShot
2) Run the application with lax sandboxing (possibly not wise)
$ flatpak run --filesystem=home org.openshot. OpenShot
3) Once you decide what directories are safe use "flatpak override --user" to change the filesystem sandbox default.
YMMV