I contacted COMSOL support. They told me that issues on Linux aren’t a priority at all (the guy I had on the phone sounded like having a native Linux version was already a privilege).
It seems to use Java, and has its own instance of a JRE, maybe I should try reinstalling using the system JRE instead of having the setup program setup its own JRE for this software only… But I’m not sure this would solve my issue.