It is affecting Windows users too - https://answers.ea.com/t5/Bug-Reports/Weird-texture-lines-on-some-objects-when-hit-by-direct-light/m...
I also have it on my MacBook Air with M1:
I thought it may be a hardware issue with AMD GPUs but my air doesn't have an AMD, even though the Config.log thinks it is:
=== Graphics device info === Number: 0 Name (driver): Unknown Unknown Name (database): AMD Radeon R9 370 and 8800 Series [Found: 1, Supported: 1] Vendor: ATI Chipset: Vendor: 1002, Device: 6810, Board: 00000000, Chipset: 0000 Driver: macOS Metal driver, Version: 0.0.0.0 Driver version: 0 Monitor: FD626D62 Texture memory: 5461MB
Little update - Simp4Sims has uploaded a GraphicsRules.sgr file that improves the in-game graphics considerably and overrides the default Mac settings. It doesn't fix this issue but I did see an improvement in my game. I posted about it here and there's a link to his site to download the file https://bluebellflora.com/2021/07/10/improve-the-graphics-in-your-sims-4-game/