There are several extensions for desktop Firefox that block the mining on sites that uses it and in no particular order are many examples: https://addons.mozilla.org/firefox/addon/nominer-block-coin-miners/ https://addons.mozilla.org/firefox/addon/no-coin/ https://addons.mozilla.org/firefox/addon/miningblocker/ https://addons.mozilla.org/firefox/addon/themineblock/ https://addons.mozilla.org/firefox/addon/nominers/ https://addons.mozilla.org/firefox/addon/coinblock/ https://addons.mozilla.org/firefox/addon/coin-mining-blocker/ https://addons.mozilla.org/firefox/addon/notmining-org/ https://addons.mozilla.org/firefox/addon/no-miner/ https://addons.mozilla.org/firefox/addon/minerblock-origin/ For extensions like uBlock Origin and Adblock for Firefox. https://github.com/hoshsadiq/adblock-nocoin-list/

The issue with adding a feature that can be covered by an extension is often times it end up being more basic or stripped down in features and may be only in about:config settings vs a gui.