I have a long standing friend through a hobby.
I mostly only see him because of the hobby or occasionally at social things with people we know through the hobby. I wouldn't say we're particularly close but I like him and have always thought him to be a decent bloke.
Recently however he (married) felt the need to "tell me how he feels". I shut him down pretty quickly, it hasn't been mentioned since and everything has seemed entirely normal when I see him with the group.
However, he has started messaging me. Not loads, maybe 3/4 times a week and always completely harmless messages about arrangements or maybe a news article on something we'd been talking about, perhaps an event the group might like to go to.
Nothing at all he couldn't show his wife, but it is new. Previously it would have been very unusual to hear from him direct, rather than in a group chat.
I'm inclined to just carry on and pretend I haven't noticed. I send polite, but not engaged responses, after a reasonable amount of time has elapsed and don't encourage any back and forth.