Discover is an app store, not a full-featured package manager, it isn’t designed to show all individual packages, nor most command-line tools. I also believe it depends on a package having correct metadata included, and this particular package may be missing this on your distro.
This is the normal Ubuntu 22.04 package, which looks to be the latest git pull at one point, back in 2018.
If your distro’s package is really that old, then it seems likely to be missing the metadata that packagekit/discover/gnome software needs to show this application. Some software applications don’t show in *buntu for similar reasons.