Snap closes after splash screen during plugin update

The log file you have attached looks fine. The tip @gnwiii write might be worth testing.
Another thing you could try is to update the driver of your graphics card.

You could also try to update SNAP to the latest version from the command line.
How to do it is explained here:
Update SNAP from the command line - SNAP - Confluence (atlassian.net)
the command would be:
snap64 --nosplash --nogui --modules --update-all