blockerDNS blocks ads and trackers at the DNS level, the benefit being that you don't need to install any apps or extensions. But for cases where you may not want to, or be allowed to, change your DNS settings, the Firefox extension offers the same level of blocking along with the same lack of logging or data collection.
You can install the latest published version from the Firefox Add-ons store.
If you want to modify the code or play around with it, you can sideload it into Firefox. First download and extract the ZIP file or clone the repository.
git clone https://github.com/tambeb/blockerdns-extension-firefox.git
Then go to Firefox's extension settings and sideload it by typing about:debugging in the address bar, going to This Firefox, clicking Load Temporary Add-on... and selecting manifest.json from the extracted or cloned folder.