vckanandvpp
https://zentalk.asus.com/en/discussion/comment/86228#Comment_86228
As per XDA developer fourm , we will get OTA updates if we unlock it unofficially. But I didn't try because I am happy with Pixel ROM.
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On Asus Zenfone 5 (2014), when the phone was upgraded to Android L from KitKat, I did install a custom rom but later I found that Asus stopped pushing me later versions (mostly security patches as L was the last OS for Zenfone 5 at that time) but when I noticed the same and posted on forum, almost everyone including MODs told me that since my bootloader was unlocked, I won't get future OTAs. After that, I relocked it, but I never received further OTAs. Thats just my experience with Asus.
It might be possible that now after these long years, technologies and systems have gone through extreme upgradation and as you said, it might be possible to get FOTAs after relocking the bootloader but I need to check the same. I am now just waiting to receive the official stable Android 10 since we over waited and after few weeks, I would try to install the pixel custom. And at that time, I would give it a try to relock again to check whether OTAs come or not because Asus would definitely push further security patches for at least next one year, so it can be checked.
