There's an ultra wide mod pack out that helps a bit by adjusting LOD distance. Doesnt eliminate it completely but much less pop in.
Pack here: https://github.com/Fl4sh9174/Switch-Ultrawide-Mods/blob/main/Pok%C3%A9mon%20Legends%20Z-A%20%5B0100F43008C44000%5D%5Bmods%5D.zip
