Your question would be better asked on XDA. The H910 has a locked bootloader that LG/AT&T never officially allowed to be unlocked. That means you cannot flash TWRP or a custom ROM directly unless you use community-made tools. - https://xdaforums.com/f/lg-v20-roms-kernels-recoveries-other-developm.5874/
Thanks. I couldn't find a systematic or step by step approach to install a custom rom on my H910.
I think this phone is probably too old to get a new live.