I downloaded MPLAB a couple of days ago just to take a look. I was pleasantly surprised to see the first steps in AVR support. Nothing works yet, but it is a start. I look forward to the day when Microsoft Windows will be a thing of my past.
When I started up MPLAB (from Ubuntu 18) while a MEGA328PB X-Mini was connected:
When I created a new project:
Import a project from AS into MPLAB: