Large scale desalination produces a lot of brine. There's no way to release it in small amounts because it isn't produced in small amounts.

You could but estuaries are incredibly important ecosystems and increased salinity might be harmful to them. Arguably the best place is oceanic areas with strong currents to promote brine mixing with normal seawater. The worst impacts are where the brine sinks and does not mix, creating a dead zone on the sea floor.

yes they do that in some facilities, it's called sewer discharge and can be quiet effective in a well monitored and designed system, surface water discharge uses a similar method of dribbling brine into the water as part of a system that uses ocean currents and tides to disperse the brine back into the ocean.

While brine return is a complicated and important step it's really not some major ecosystem destroying problem in any of the modern installs - it's just important to model and monitor the system, the same way sewage systems find a location where currents carry stuff away and allow it to disperse brine return systems do, with brine it's just stuff that belongs in the ocean anyway so it all mixes back in fairly quickly.

A lot of people seem to like to learn the difficulties involved in a new tech and then just use negative thinking to exaggerate it into a reason the tech will never be useful even after decades of improvement and investment. There are huge projects around the world which have done really positive things for local ecosystems, they're even refilling the sea of galilee after decades of over extraction and allowing groundwater levels to restore.

The brine from this system is not very concentrated

Sounds good to me

When I first read about this I thought, why not outflow into a tiered salt mine and let evaporation do its thing