well, as discust here “Impossible to igonre Landscape collision without also ignoring "world static"?” it is just impossible to use a different channel in landscape.
you can set it via editor, at runtime it will always be “world static”, so you need to consider world static as your landscape channel.
What I did, in my building blueprint where I have my building mesh, I have a box that change the player profile on overlap, to a profile that ignores world static, and when it leaves the area it change back to pawn.
the thing is, just make sure in this area you have something else to hold you from free fall, like my blue print meshes are set as world dymamic.
I use this to cut a “virtual hole” trough the land scape, paint that area invisible with virtual texture, and using the profile to ignore world static so you can pass right trough it while inside the buiding.