I don't like assumptions, so I just reinstalled the ezviz app to try, because I never needed to turn it off actually and unfortunately, while the option is present, it doesn't work when you turn it off: error "operation failed, server exception".
So the "Outdoor Bell Sound" option doesn't work with hikvision firmware. Must be a specific feature added by ezviz in their firmware, that explains why the other mobile apps (Hikvision, Guarding Vision) don't have the option. This could be added to 101 (
@David L).
Regarding the firmware update: I don't recommend upgrading fw automatically if you use another vendor's firmware, better check manually here in the forum every once in a while. I bet EZVIZ app obviously
downloads ezviz firmware, but it's an assumtpion, and I don't even know how I could try. Right now the EZVIZ app reports that I'm using v5.2.4 build 200321, which is hikvision's latest fw, and it tells me there are no updated. But I would never dare to upgrade it this way. I suggest to disable automatic upgrades, unless you stick to the same vendor's hw/fw combo.
Thanks to your good questions we learned something new.