Fix long-standing issues that create headaches for new users. I’m not sure if it’s Mint-specific, but:

Backing out of the OS installation should not make it crash to the point that I have to rename a file in the USB to fix it.

Downloading the new video codecs while installing the OS and ticking some box should also not make it crash.

And warning me beforehand that I need to disable secure boot should be a must.

Fix that and you just saved your users three attempts at installing and a couple of hours of troubleshooting just to get their feet in the door.