[LineageOS Questions & Answers] cannotdraw:
it should be possible

Has anyone figured this out?

I too have devices on ting, fantastically built devices that run amazingly thanks to a solid construction, the support of many many developers who are craft some of the best ROMs for any device I've ever seen, considering the limited specs of the XT1031s. Fortunately/adequately enough though, they only run on 3G Sprint, Boost originally, moved to Ting for their great rates for FreedomPop customers when they bought them out.

Anyway, currently to get a device on ting, I have to flash the latest 5.1 official stock Boost Mobile Rom with the latest radio baseband and firmware and such. A process thats pretty involved. I'm hoping that I can backup the stock image using TWRP, as when I went through the process of reloading the official image through the individual files via mfastboot, I skipped the logo and recovery files, and since I was able to retain my custom logos for boot and bootloaderunlocked screens, and the recovery, I'm hoping to be able to make an image of the stock ROM, which if at all possible, I'm going to do my best to make as bare bones as possible. May start with flashing the bloatware removed version of stock thats available, then going through and removing basically every app on the phone with the exception of settings and anything to do with phone, phone/carrier services, sim toolkit, etc, so I can have the smallest image possible that could maybe be restored everytime/anytime that I want to update the PRL or Profile. Which it looks like theres a new version of each released at a minimum every 3 months, as I just activated another device this way and there was only an incremental update of the last digit. If this works, great. If it doesn't then I hope that theres an answer to the question in the initial post of this thread;

Is there a way to update the CDMA PRL and Profile on a device that is running a custom ROM? If so, is it something the ROM needs to specifically support or is it something that is possible to do with a bundle of apks? Like sim toolkit and the like?

If its ROM related, are there, or would it be possible to take the necessary components from the stock files and install them in Xposed or Magisk? Or perhaps the buttons in the settings panel of the stock rom simply executes a series of commands that can be executed within a terminal CLI on the custom ROM? I assume that since the custom ROM clearly has access to the 3G radio since I can make and recieve calls, I have data, and text messaging (haven't tried MMS, but I assume it works) so why couldn't it do one more thing and initiate the PRL update?

I assume that even the stock rom doesn't ever touch the PRL or Profile, seeing as they remain even after a user data wipe, and are available for the radio to continue to use with custom roms, which means that the radio chip has to be the one storing the PRL Profile, so I bet that the radio also directly downloads those files from the carrier when asked to do so, and the stock rom must only come into play for the base logicstics of it all such as radio-"is this prl/profile a newer version than the one that i have now?" and phone-"yes, download new, purge old, flash new, tell me when done and leave me alone" Since the radio doesn't have its own processor for those sorts of things perhaps? If thats the case, then that should imply that theres nothing particularly proprietary or licensed, etc, that a rom would explicitly need to have in order to initiate these updates since it would never directly need to touch/see the files, just know that they were updated and what version number they are. What also lends me to believe this is the case is the fact that you can't select to downgrade the prl/profile, rollback, or load one manually, at least not that I can see.

So basically I'm saying that I hope it should be something simple to do. And if it is simple to do, you would think that custom roms would be able to read the carrier correctly too? Right now my new device reads "Boost" still. My previous one when I got it on ting I wanna say actually read ting afterwards. But when I loaded ressurrection remix, I had no cell/data/voice nothing, It just kept asking me for a sim card, which this phone doesnt have at all. When I loaded Lineage, everything cell related work. But can't update prl/profile, and carrier reads as "3G Roming Indicator Off" Which idk why thats the case.

Perhaps I'm missing something

Perhaps custom roms are missing a few somethings.

The only sure thing is that carriers need to just not be so greedy/dumb/uselessly difficult, and make giving them money for service easier, preferably without questions. Or at the very least actually provide some security so all this nonsense is at least worth something in the end to the end user, instead of being done so that they can try to spy on your unencrytped texts and calls to sell to advertisers, and selling access to the higest bidders such as the government and bounty hunters, whilst preventing you from restricting that information.