Your state may vary. TL;DR: Be polite, don't draw attention to yourself.

I've been told to wear a mask at a restaurant (for the 10-second walk to an outdoor table), at an auto repair shop, and at a hotel check-in desk.

I typed up a fake doctor's note, and held it in my hand upon entry. (I also carry an inhaler that an asthmatic friend gave me. Honestly, wearing a mask would probably be less work but this is about principle.) The guy at the restaurant was polite, but when he asked me to put on a mask I explained that I had a medical issue and showed him the (folded) doctor's note. He didn't press the issue.

The auto repair shop, same thing. I never had to show the note. (I know they have no right to ask details about my medical condition, but I went to the trouble of creating the prop so I figure I might as well have it with me.)

The bitch in the hotel was a little different, raised a stink. I showed her the note and she backed down.

Yesterday was the big test, the supermarket. I walked confidently in. An employee even greeted me at the door. I admit I had my nose buried in my phone while shopping, but as best I can tell, I wasn't getting any dirty looks. I was literally the only freeface in the store. I must've been in there for 20 minutes. The girl who checked me out couldn't have been friendlier, as was the bagger. NO ONE SAID BOO.

I was ready to tell anyone who asked (EDIT: Any employee who asked) that I have a medical condition. There's no counter to that- if you physically can't wear a mask, you can't wear a mask. Then again, it is private property and they have the right to refuse service to anyone. If asked to leave, I'd have said, "Just so I'm clear: Are you denying me service because of a medical issue?" If I'd still gotten pushback at that point, I'd have left.

I don't wear my GEOTUS shirt in these places. I don't open carry. I'm not going to paint a target on my back. And if asked to leave, I'll leave. The people you see on YouTube throw tantrums in the store and start screaming. Don't be like them. Be understated but confident, and at least in my state, you won't have to wear a mask regardless of what our idiot governor has to say about it.