I think you can force the game into Canvas mode using the Community Basic plugin, which should let you debug the issue.
To make the game run in WebGL mode on more systems, you can replace the runtime with a current 'normal' version from https://nwjs.io/downloads/. This also improves the performance considerably on all systems, as the runtime that comes with MV is from 2018 and Chromium is about double the version number now.