Is it possible to install the new stock firmware through twrp?No you can not. The phone might download a OTA but it will fail to install because it needs the stock recovery to install it
Can I flash only the recovery and check for updates? If I flash the complete firmware, does exist the possibility if it becomes again sim locked?Download and flash this zip in RUU mode. It's the stock firmware which includes stock recovery. You could also extract the stock recovery .img out of it and flash it from fastboot.
http://xda7.androidrevolution.org/db_mirror/Firmware/HTC/HTC_One_M8/401/1.54.401.10.zip
Posted via Android Central App
I thought it could get locked again, because it is not unlocked by code but with some method using root and custom recovery. Thank you very much for your help!The firmware that you provided is the unlocked model as it is. This should not become sim locked either way. Once a phone is SIM unlocked it can't go back. And yes. I use 7-zip for extracting the recovery out of firmware.zips
Posted via Android Central App
Can you tell me how I can do that, because I don't want to screw something up?No prob. Just make sure after you fastboot flash recovery.img that you fastboot erase cache to make sure no partitions get screwy. Just a precaution
Posted via Android Central App
I did that sometimes, just flash the recovery and I'm done? I want to get the update through ota I wouldn't like to install it manually.You know how to use fastboot commands?
Posted via Android Central App
Is it possible that my phone can become sim locked again? I guess the radio versions update too?Yeah, flash the recovery and you're done. As long as you're on the stock kernel you should be able to receive your ota.
Posted via Android Central App