Re: I hate to say it...
your options are greater than that, there are Android phones available with removable batteries, and even some by samsung, and far more Android clones that are stable, as is always the case with OSS that matures.
Also there are security tools available for android, that dont have a comparable for iOS as Apple wont make the access needed possible.
Thats the big difference with Android over iOS, Android will run on any hardware that wants it to, feature availlability is goverend by market forces, and the numerous mods actually drive improvement in the base OS.
Your iPhone 6 running iOS 8 was behind Android 5.1.1 there weremultiple options launched that year from Samsung,HTC, OnePlus, Sony, Huawei and others. the Galaxy S6 on 7.1.1 (its latest update) is probably more feature rich than your iPhone on iOS 12.4.8
Unfortunatley, your phone also has the Checkm8 hardware vulnerability which is unpatchable, and if it was in an android phone would have been found sooner.