All Snapdragon variants of Samsung's Galaxy lineup are locked, regardless of carrier. This has been going on at least since the S7, and there are exploits to unlock bootloaders for such phones, at least as far as the Note 9 [1]. I would argue that if you need an exploit to unlock the bootloader, you are no better off than purchasing Apple.
It's still a far fry from "no better," in my view. There's an ecosystem of Android software for these environments. For instance, LineageOS, as the typical first target, was unofficially ported to the Note 9 Snapdragon soon after the bootloader exploit. There are also existing tools for Google Apps, microG, Xposed, etc.
Admittedly it's been a while since I've been on a jail broken iPhone, but AFAIK custom ROM support is almost completely missing from iPhones. The jailbreaking ecosystem there is more comparable to Xposed tweaks and root access on an Android device. Custom ROMs are far more extensive with their own software and theming frameworks, perspectives on usability and performance, and often completely different OSs (that are not Android) thanks in part to GSIs these days.
