Since updating to .21 the Nether doesn't render out to 24 chunks as defined in the Video settings. It seems to be rendering only out to 8 chunks. The Overworld seems unaffected. 

Update: Recently started using a new RTX pack called "RealSource" and discovered something odd - when using the 512 bit resolution pack the render distance is still bugged BUT when using the 1024 bit pack the rest of the chunks are getting rendered as intended. I can't make heads or tails of this. 

It's worth noting that when loading either pack I get the low memory "fallback" error/message.

This screams "memory management" but what I'm seeing is counter-intuitive...   

The first screenshot has plant blocks displaying 16 bit textures but the render distance is only 8 chunks 

As seen in the second screenshot where the 1024 pack is loaded, the plant blocks are displaying low res textures (8 bit?) but the engine is rendering out to 24 chunks. 

Hope this helps.