In general, you are going to have trouble getting a desktop launcher to run with strict confinement.
Snaps cannot normally launch other snaps or host system applications. You also don’t generally have knowledge of what other applications are installed on the system.
There is some (unfinished) work to provide an interface plus support infrastructure to implement something like this, but it would require the application to be built against the API:
At present, classic confinement is the only functioning alternative.
