Do you live in a community where social pressure is a thing? Or is it big enough that nobody knows anybody? If your landlord won't listen to reason, you might be able to use social pressure--get friends (so your landlord can't blame you and make your life more difficult) to start posting in facebook, nextdoor, etc about their poor immunocompromised friend (include any details that might make you more sympathetic up to and including a picture with your cute child and/or pet) whose life is being endangered by having hordes of strangers trooping through his home. Let that pass around for a bit, then send your landlord a concerned message: "I'm so sorry, I talked to some friends about how worried I was about having random people in my home during a pandemic, and I didn't expect it but they posted about it and now a bunch of people are mad at you. So sorry, I never expected they would post publicly about this. I guess it looks pretty bad for your business., since people don't want to rent from landlords who don't respond to tenant complaints."

Unfortunately, this strategy requires you to go public with your health status and play for pity, but it's the only way I can think of it hurting your landlord's bottom line. If nothing works, I recommend making everyone who comes through your home feel very uncomfortable by making it very clear that they are endangering your life. This won't protect your health, but spite isn't nothing. Wear the most elaborate protective gear you can think of, post a sign on your door explaining your health status and requesting that they sanitize their hands before entering with the sanitizer you have sitting there. You might also supply disposable masks. Some people will probably decide they don't want to tour your home after all and turn around at the front door.