I am an American living in Switzerland in a rental unit (top floor - building roof is above).

The master bathroom is on the fifth floor and has a wall-mounted toilet.

I just moved in, and the toilet has a sulfur/sewage smell. I've owned a home before and experienced this in the U.S. when the o-ring on the toilet goes bad and needs to be replaced, and sewage gas comes up.

Unfortunately, this is obviously a different sewage set up, and with the wall mounting, not something I could address even if I wanted to.

I had a handyman come to take a look, and of course, the smell wasn't there that day. He also said there could be no way I'd be experiencing those smells with the way the toilets work here.

I tried to pour in the Swiss equivalent of drain-o thinking maybe it was bacterial, but it didn't work. Maybe need to try again?

Hoping someone can help me pinpoint what the potential issue/solution could be here. I can engage another handyman, but if they're not smelling the issue, I want to be able to explain the problem and the solution I need given the last guy.