LibreWolf is a great privacy oriented Browser for desktop. But there is no version for android or IOS . There are some like mull but they have their own problems. Mobile phones stay with us most of the day. So we need extra privacy for it.
This always gets downvoted, because it's a painful truth, but Chromium on Android is significantly more secure than Firefox.
There is a reason why the default included browser on GrapheneOS, Vanadium, is a Chromium fork.
So I'm sorry, until Firefox on Android catches up to Chromium, another Firefox fork isn't going to make the impact on the ecosystem that you think it is.
I'm not saying you can't or shouldn't use Firefox forks on Android, I'm saying do so being aware of their limitations relative to Chromium forks, such as
Cromite, or Mulch, the latter being the same dev as Mull. That same dev also has a lengthy write-up going over the technical details of why Chromium is more secure than Firefox on Android.
This has nothing to do with desktop browser engines, this is specifically and exclusively in regards to Android browsers
While DivestOS includes a Gecko based browser for privacy reasons, Chromium based browsers have many security advantages. It is up to the user to choose their preference.
Pretty sure I told you where you could find more information, as well as pointing out that the default browser on Graphene is a hardened Chromium browser, not Firefox Gecko.
But okay, here, I can even do that little bit of searching for you:
it really sucks tho, because most chromium forks still force you to use a google account in order to sync, and thats if they don't strip google entirely. there's brave, but I haven't had the best of experiences with that browser.
I can still self host something like floccus to "sync" bookmarks, and use kde connect to send browser tabs from one device to another, but I still wish it was as convenient as firefox; which iirc, let's you self host their sync service
Per-site process isolation is a powerful security feature that seeks to limit exposure of a malicious website/script abusing a security vulnerability.
Firefox calls per-site process isolation Fission and is enabled by default on desktop. Fission is not yet enabled by default on Android, and when manually enabled it results in a severely degraded/broken experience. Furthermore Firefox on Android does not take advantage of Android's isolatedProcess flag for completely confining application services.
Standalone Chromium based browsers strictly isolate websites to their own process.
Personally I would argue that allowing users to install extensions, mostly adblockers, you remove what's probably the single most common real world vector for attackers, ads. So while chromium browsers may be more secure I would say you're probably less likely to run into a problem with a firefox based browser with ublock origin on it, mobile or desktop.
Cromite a Bromite fork with ad blocking and privacy enhancements; take back your browser!
Also, Mulch lets you pick your DNS provider. So even if you don't already have system, or network, wide ad blocking, it's not like you're deluged in ads.
Again, I'm not saying no one should use Gecko based browsers, I'm just repeating what developers of respected hardened security ROMs have written about. Actually, that's not true, I'm taking a softer approach as the GrapheneOS wiki/FAQ says NOT to use Gecko based browsers.