The only real “problem” would be the lack of certifications, which are quite hard to get.
Real Time Operating Systems (RTOS) are normally used for these tasks, but, AFAIK there are already projects using linux with patches to make it run a RTOS kernel.
In my opinion, I think it all depends on what part of the plane it is running. If it is a core sensor, providing real time data, it makes a lot of sense to use a RTOS. It needs to prove it can run its tasks on time, and the scheduler needs to be understandable. There’s also a lot of overhead with running a full OS with processes, which don’t make sense for a sensor which only function is to provide data over a CAN/LIN bus.
But, for other things, like dashboard visualizations, music for the aircraft, entertainment, and those non-critical-realtime needs, then it makes a lot of sense to run linux. After all, you’d get access to a lot of already built software and a working dev environment.
And don’t get me wrong, this is clearly BS from boeing to keep selling their closed source software. There are already open source RTOS systems, like FreeRTOS. I do not mean to keep those real time systems closed, but to use a full OS where it makes sense and a RTOS where that makes more sense. Both open source!