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The experimental Mozac/GeckoView-based browser #SmartCookieWeb-Preview can also install/sideload a xpi-file by url (Settings > Advanced settings > Sideload XPI).
No option to enable the add-on in private browsing though.
https://github.com/CookieJarApps/SmartCookieWeb-Preview/releases

Or switch to #Kiwibrowser (Chromium)
https://play.google.com/store/apps/details?id=com.kiwibrowser.browser

or use the adblocker filter/userscripts
https://gitlab.com/magnolia1234/bypass-paywalls-clean-filters