Oppo/Oneplus are systematically scrubbing all traces of the older OTA fw from all the known sites. This is why i havent made any updates to that thread for doing region swaps. My instructions still stand firmly for how its done and whats required, but now its kinda on a peer to peer basis, cuz all the OTA links that are now available anywhere have a new signature check that will make the fw not appear or fail flashing if you try them. But the steps still work... and Creeper36, if you came from a T-mobile original device, you do not want to take that next upgrade ... you CAN go up to A.12 and you will get your 5g , wifi calling, and volte all working... but anything A.13 and above will lock up all your apps and the only way to get the phone working again, is a factory reset, and a rollback. Some security function has been activated that can detect you original device fingerprint, and if you are on ANY fw other than a 2419 build, it triggers the app lock.
Im still working on finding out what needs to be removed from the CarrierDevicePolicy so that this doesnt happen, but i need root access to make progress, and i am on one of the newer 10T that have the Fastboot Protocol disabled. My advice would be to just search thru the oneplus community pages or go to the telegram/discord channels... both are user operated, so you can message someone or just ask the group for the file you want and chances are someone has it, who can help you. I have A.15 but its for the 2415 build. All the fw you find below that version on the common sites (gsm mafia... etc) are packages you will need the msm tool or qfil to flash.
