You found one solution but that doesn‘t mean it‘s the only one. And it‘s a pretty grim one because it‘ll be far less performant. Unless you are hard pressed for time I‘d play with some of the urp, graphics, quality, player and specifically lightmap/shadow settings to see if there‘s an easier workaround.
And let‘s not forget, Apple has a long history of [undersupporting WebGL and taking an unfair amount of time to fix issues on their end]( iOS 15 + WebGL 2 issue page-2#post-8001036). And [also this post]( iOS 15 + WebGL 2 issue page-2#post-8061206). That same thread has a number of tips and potential workarounds you could try.