Firefox users from the United States will have the web browser's DNS over HTTPS feature enabled by default in the coming weeks . Starting today, Mozilla is going to roll out the feature to users from the United States.. for more info go here https://www.ghacks.net/2020/02/25/mozilla-rolls-out-dns-over-https-for-users-in-the-us-on-by-default/#comments
How to Enable DNS Over HTTPS in Firefox
https://www.howtogeek.com/659252/how-to-enable-dns-over-https-in-firefox/
Here's how to enable DoH in each browser, ISPs be damned