Due to the way Drupal 8+ operates, the vast majority of 8 applies just as well to Drupal 9 and Drupal 10 too but this might not be evident for newcomers. What do do here?
I think most of the times you'd simply leave the tag out and instead tell in the question body what version of Drupal you are currently working with. The farer away we get from Drupal 7, the more irrelevant the version tags will be.
And then you'd only use version tags for when something is really specific to a certain version. Like when something changed between Drupal 9 and Drupal 10, and you want to know how to make it work in Drupal 10, because the way how it worked in the past doesn't work anymore, you'd tag your question 10.
This also complies with the usage guide of each version tag: You should not use it to tell what version of Drupal you are using, you should only use it when asking a question that is specific to just that version.