Turning on DNS-over-HTTPS in Firefox v.74 on Ubuntu 18.04, 19.10.

DNS over HTTPS (DoH) is a protocol for performing remote Domain Name System (DNS) resolution via the HTTPS protocol. A goal of the method is to increase user privacy and security by preventing eavesdropping and manipulation of DNS data by man-in-the-middle attacks[1] by using the HTTPS protocol to encrypt the data between the DoH client and the DoH-based DNS resolver. Encryption by itself does not protect privacy, encryption is simply a method to obfuscate the data. By March of 2018, Google and the Mozilla Foundation had started testing versions of DNS over HTTPS.[2][3] In February 2020, Mozilla rolled out a version of Firefox browser that encrypts domain names by default for US-based users.[4]