Looking for a wireless intercom system with local power supply

Wifi with WPA2 is just as secure as Powerline.

MAC addresses can be easily changed, but first you need to know the approved devices.
No one stands in front of a normal residential house to hack the Wifi.
The devices within the LAN should also be secured.
With, for example, Radius I have only mentioned some possibilities for further securing. Many devices support this. At the latest when you have a NAS, you can set up the RADIUS server.
Hampshire wants a "simple" solution.

The only devices I know for Powerline that are suitable for outdoor use are the hotspot from Bega / Devolo. In other words, a device from Devolo inside near the FritzBox and connected to it. Power line to the doorbell system and plug the hotspot in there. If only the app is used, the guest network (LAN 4 and activate in the settings) of the FritzBox could also be used for this. This would also protect the LAN. Advantage would be internet access also in the garden/driveway.
But for that money you can also get enough CAT8 cable....

sorry, what the hell do you want to do with CAT8 cables? Connect a data center to a brick gatepost just like that?! Range well under 100 meters, damn hard to install (bending radius) and you can't take advantage of the data throughput benefits because the connectors can't be crimped by any private person and are not supported by any device anyway.

For such a video cam, CAT-5e is more than enough, these are easy to install and cost almost nothing. Would be my favorite instead of such a jury-rigged WLAN solution.

Can I tell you why. It has a cable length of approximately 100 meters. If you lay new cables today, you use CAT7 or directly CAT8, depending on price and availability. For 100 meters in length, I would especially pay attention to the shielding. It’s not about needing a 10gbit connection at the fence sometimes, but rather reliably achieving 1gbit or 100mbit. When laying the cable, there is no big difference whether I use Cat7 or Cat8 patch cables. Connectors in this application are not Cat8 anyway...

Data security / transmission rates - it remains an intercom system without requirements for security or high availability. I have now decided on a wired solution, probably Auerswald, as it is available at a low price with 3 doorbell buttons and without a camera with connection to a/b port. Thank you very much for the advice.

Cat 8 is basically like shooting at chickens with atomic bombs in private cases...

By the way, CAT8 officially has a maximum cable length of 30 meters, which is quickly exceeded in house construction.

Cat5e is more than enough here, it is specified for up to 100m and has 1GBit/s. That is completely sufficient

I didn’t say anything about using CAT8. Cat 8 is standardly better shielded. He probably won’t need that at the fence in the future either. 100 meters (or more) with 1 Gbit are easier to achieve with Cat 8 than with Cat5e. Whoever installs CAT cables today should choose 7 or 8. But hampsire has now found a solution for himself.