I am sure that there will be people that think like you there too. Look for the oddballs, the ones who are not 'included' in the social framework and you will find your tribe. You do have to be strong though.

I'm in a small town and also I am reclusive. I would dearly love to find one true and faithful female friend who loved discussion and liked the same things I do. Senior Centers around here do not cut it. They all pray over food, say the pledge, and believe in Trump. I found a big audience today with 4 or 5 different women just by going 30 miles away to my dentist.

Have you noticed there are many, many, many more conversational topics than religion or politics? Did you know that up until just a few years ago it was considered Incredibly Rude to bring up/discuss those subjects?
Unless you enjoy confrontation, feeling bad/making others feel bad, why not discuss other things?

Retired? Who or what persuaded you to settle in a small town?

I looked for better conversations in places like The Unitarian Church or Meetups involving my interests. Don't look for it on SM, even from what were once close friends, but I suppose it can happen.

Join groups who do activities you enjoy. Rock hounding, bird watching, bowling, hiking, etc. As a Democrat, I attend Democrat "coffee breaks" twice a month.

That's a great way to meet like-minded men and women.

Long long ago I gave up trying to "convince" anybody about the non-existence of deities. I found it to be actually counter productive. Because they try to convince me of their beliefs. Instead, I never initiate those kind of conversations. And if necessary, I respond with the lowest-key, fewest words like "I don't believe any of it." At other times, I'll say, "It's all make-believe" in a calm voice. Then I stay as quiet as possible. Or change the subject. I recognize that people are very emotional about their beliefs.

Is there a local bridge club? How about considering a local civic club like the Lions' Club?

My story is similar to yours, however the crowd that I immediately got involved with were the local artists (I'm a photographer that sells landscape photos...) I've found that such people tend to be more left of center than the surrounding neighbours (as nice as they are) to be right of center - church-going, camo-wearing, quad-driving kind of folk. I wear some camo TBH, but I also sport a long ponytail!

You will probably have to find your like-minded friends online or drive to a Unitarian church wherever the closest one is. Or find a meeting of Atheists and Freethinkers by looking online for where the nearest meeting is, and attend those. That's the price of living in the sticks... It appears that you live somewhere in rural Washington state. I live in a decent-sized metro area, but unfortunately, it's in the middle of a hick state full of farms, so I am in the same boat as you as far as dating. But at least in my area, it's not that hard to find some intelligent non-believers. The problem is that at my age, they are mostly already taken or coupled up.

Another way to maybe meet some intelligent, offbeat people is to check out a local community theater group, wherever the nearest one to you is. When I was young and living in a new town, that was where I quickly found a group of like-minded people for friendship, even if it didn't have anyone for me to date from the group. They were mostly older than me, but fun to party and hang out with.