How many times a single select choice has been selected?

Hm, I'm not sure I fully understand you, sorry.

If you've got a bunch of records now and you want a count of the number of records that have each option selected, grouping the records should give you data

If you're talking about a running count of the number of times a single select option has been selected, e.g. for Record A I select `Option 1`, `Option 2`, then `Option 1` again, and you want to know that `Option 1` was selected twice, then I think we can't get that kind of historical data

You can put something in place that'll start gathering it for you now?  I'm thinking an automation that triggers whenever the select field is updated, and conditionally adds a character to a specific field based on the selected option

So if your single select field has `Option 1`, `Option 2`, `Option 3`, you'd have three separate fields to track them:
1. Option 1 count helper
2. Option 2 count helper
3. Option 3 count helper

And whenever a user selected `Option 1`, the automation would update the field `Option 1 count helper`with it's existing text and then an additional character

So:
1. User selects `Option 1`
2. `Option 1 count helper` gets updated and its new value is "1"
3. User selects `Option 2`
4. `Option 2 count helper` gets updated and its new value is "1"
5. User selects `Option 1`
6. `Option 1 count helper` gets updated and its new value is "11"

You'd then have a formula field called, say, `Option 1 count`, and its formula would be `LEN({Option 1 count helper})`, which would output the value "2", giving you a historical count