How likely is there life in the super salty underground lake on Mars, when there is no life in the Dead Sea because it is so salty?

there are halophile (salt loving) bacteria in Dead Sea. https://en.wikipedia.org/wiki/Halophile

I've never been to the Dead Sea but the Great Salt Lake is loaded with brine shrimp and the plankters they feed on.

So there's a lake on Mars. Big deal. We know nothing more about Mars than we have done for a hundred years or so. No-one has the faintest idea, and we probably never will have, if there could be any life there. If there were, it would with 100% probability be "not as we know it", or indeed, nothing that anyone could have imagined.

Actually the water bear (here on earth) can live in that environment.

The scientists would be looking at bacteria, one celled organisms and other items that are in the primitive stage.