We can observe what is beyond the edge of our galaxy. Our telescopes - like the Hubble and Webb - are powerful enough to capture the light of distant galaxies and from that we can see that they are made up of stars just like our own. The Ultra Deep Field is one of the most awe inspring photographs ever taken - each dot of light another galaxy out there like ours.

Too far beyond that, though, and we don't know. There is an edge of the observable universe beyond which we know nothing - the universe literally isn't old enough for light to have reached us from anything beyond this horizon.

We guess that there is nothing special about this boundary and that whatever lies beyond it is the same as what we can observe, but its just a reasonable guess as we can't have any direct observation.