Using device's font option is needed(like Samsung browser). Desktop Firefox has this option. I don't know why Firefox for Android doesn't. Please develop this option. Cheers.
Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.
Thanks for your feedback! We're working on updating Firefox on Android to use system fonts. You can follow it here: https://github.com/mozilla-mobile/fenix/issues/22692
Your idea has been shared with our product team, and we're happy to report back that the feature is 'In development' at the moment. Check out @topotropic's comment for more info and stay tuned for updates 😃-The Community Team
Great job all around! This was delivered in Firefox 105 - give it a try and let us know what you think.
Looking forward to continuing to collaborate with you all here 🙌