You forgot to mention the most important thing. If it is important then it should work despite the internet and ideally, despite the LAN/WLAN. My home doorbel

You forgot to mention the most important thing. If it is important then it should work despite the internet and ideally, despite the LAN/WLAN. My home doorbell triggers a battery backed chime as well as all the other funky stuff. The chime is always first before our phones and the Sonos thingies go berserk. I monitor the battery on the chime too because the Home Assistant tells me to on a schedule. I use my multimeter. If I am down the garden, I can't hear the chime but I have a phone on me normally and the lights on the summer house blinking in morse is a give away if the mower is drowning out the phone. Tools for the job. ... Yes I do have quite a lot of time on my hands ...