There was a comment here about replacing pressurized air cabins with sealed air cabins that use the same air pressure as external atmoshere, but enriches the air with oxygen instead of pumping more air.

This requires a whole lifecycle management to keep CO2, O3, water vapor, N2, pressure, ... values correct as the passangers breathe and other events happen.

Oxygen and other gases can be obtained from usual sources or maybe from outside the aircraft, there are ways to pump a lot of air inside and filter specific gases from it.

As expected, I have no idea how viable all of this is, but it may be able to reduce a lot of weight, costs and maintenance given pressurization is a very hard to implement.

Some related reading:

https://www.planeandpilotmag.com/article/flying-high-unpressurized/

https://www.aircraftsystemstech.com/2017/05/aircraft-oxygen-systems.html