Endeavour is great, I daily it and as a Linux noob it’s been very forgiving. My only annoyance is that I’ve been having some issues with the display where sometimes I’ll wake it up and will only get a black screen and no means of doing anything to fix it. My laptop also really doesn’t like me using any other DEs besides Budgie.
Proprietary, as in, branded specifically to the airline itself. Like a Allegiant credit card, for example.