Thanks for your response :)
The best approach is to use VLANs. You can create one VLAN per network segment. Then use one SSID. And when a user connects, assign him to the correct VLAN. The downside is that if someone visits a different site, they won't be able to use the local printer. But that may be a good thing, because they also can't see _any_ devices on that network.
I have tested VLANs, but I need to share local resources between houses (printer and storage, for example). This is why everyone is in the same subnet. By my tests/research I just can achieve this buying a new device that has routing ip policy (so I could still have intervlan routing using interfacevlan and the default static routing set to this new device could route packages properly (but I'm trying not to spend extra $$$ with a new router).
If you want each users *public* traffic to go through their own LTE/4g antenna, then VLANs are the best solution.
Yep, this is my main goal: allow roaming wifi between houses but respecting the LTE/4g antenna each person's belong. This is why I thought that setting up pihole as freeradius+dhcpserver could let me send IPs+Gateways based on the specific house login. I would just have 5 shared users: house1, house2, house3, house4, house5 Everytime some device using house1 login try to reach one AP the freeradius+dhcpserver was going to return a valid ip from their IPpoll Ulisses