It will be respectful if Asus will announce end of life for devices, I mean to say something like "guys, this is last update, don't expect anything else". E.g. take a look on ZF6 subforum - obviously device is abandoned, despite having actual software, Asus doesn't want to update security patches. But users still expect something. Lol, my old tablet on A10 has newer security patch. Asus should take care more about customers, because these guys pay money for asus devices and with that attitude from company, next time they will think twice regarding which brand to select.
Yes completely agree with you. Asus should announce if they want to or already end software support for any of the models. I am using Zenfone 6 and since 3-4 months many users have asked about the software support for Zenfone 6 but none of them respond in this regard.
Also it will be useful to send manuals to users how to kill SystemUpdateService and maybe other services, which are no longer relevant for devices, which will never receive update. I understand, it's not your RAM and battery, but you may take some care for your users.