Have you seen this desal operation in Australia?

https://en.wikipedia.org/wiki/Sundrop_Farms#/media/File:1604...

It's a farm in the middle of the desert that gets all its water from desalinated sea water powered entirely by an array of mirrors.

I'm fairly skeptical of massively expanding existing RO operations due to how we tend to handle brine - which (from what I've seen) is usually just dumping it in the general area we pump from.

However my past concerns for altering seawater on a planetwide scale are much abated. Rising sea levels and glacier melt have put an end to that.

Better membranes and renewable-powered desalination plants are not going to do anything about the waste problem. Has there been any progress on that?

Brine disposal has always been my concern. I haven't come across anything promising but I'm well out of the loop.

wouldn't releasing brine into the ocean be viable with a suitable dispersal mechanism? Or are there additional chemicals released from the plant?

Yes. We already do this for all sorts of things, including sewage. (https://en.wikipedia.org/wiki/Marine_outfall)

Can't we just have giant "salt plains" where we allow the brine to evaporate and we just collect the remaining salt/minerals?

Maybe I'm crazy or not informed enough, but I always thought this water-desalination thing was a solved problem. Then I got confused when they talked about how there is "brine waste" and it's a huge ecological problem. Why do they stop short of full evaporation of the brine?