Understood, but it seems a significant enough change to warrant a bit more attention than being buried in a list of new config defaults. And though I did run app:update, it wasn’t completely clear to me what I was really agreeing to. Kind of like the programmer’s equivalent of Apple’s Terms of Service. 
Thanks for this. I first learned of Turbo when visiting the Stimulus forums while trying to solve this very problem. What I can’t seem to get confirmation of (though every indication points to it) is whether Turbolinks has been or will soon be deprecated. If so, then it seems best to leave the default config settings for 6.1 as they are, then install Turbo and have it take care of submitting forms via AJAX. Though I’m not looking forward to the inevitable ‘derailing’ this causes (which should be the preferred term for Rails upgrades gone bad), like how to get Turbo to work with Devise.