A bathroom that repeatedly smells like sewage despite cleaning deserves attention.
Pouring salt into the bowl might temporarily make you feel as though you’re doing something, but it doesn’t address the source.
If the smell persists, have the plumbing inspected.
Can Salt Damage Your Toilet?
Ordinary table salt isn’t likely to destroy a toilet simply because a small amount was placed in the bowl.
However, that doesn’t mean more is better.
Salt is abrasive.
Repeatedly scrubbing porcelain with coarse materials can potentially contribute to surface wear or scratches.
More importantly, large quantities of anything should not be intentionally flushed down a toilet unless you’re sure they’re appropriate for the plumbing system.
Toilets are designed to handle human waste and toilet paper.
They are not garbage disposals.