Everyone knows the dangers of the activities they are partaking in at this point. If someone chooses to go to a restaurant there is a chance they will catch the virus. Same for every other activity.
If you are so worried then stay home for ever. Business shouldn’t have to be worried about lawsuits when they reopen.
Businesses need to take matters into their own hands and purchase insurance, warn customers, or actually undertake safety measures. Otherwise, customer should be able to sue. Same as any other liability. If you don’t want customers to sue, and want to be open, it’s your responsibility to ensure that nothing happens or that they can’t sue/you’re covered.
A simple sign stating “we take no responsibility etc.” and basic insurance policy should suffice. Or- here’s an idea- actually show adequate safety procedures.