pfsense

I'm trying to get my new Dreamtech L10s Ultra (robot vacuum) to be discovered by Home Assistant, but they're on different subnets and I found an explanation that there are sometimes problems discovering devices across subnets. This seems odd to me because the Xiaomi Miot Auto integration in Home Assistant saw my L10s and even knew it’s IP address - but perhaps that’s TCP and the problem is that UDP can’t cross subnets?

The article says there are 2 ways to possibly overcome the cross-subnet issue: put the devices on the same subnet (currently not an option for me), and “configure IP masquearding on the outgoing routing interface for the subnet where the MI device resides.” With GPT’s help, I tried to add IP Masquerading (which I guess is just NAT), but it’s not working. I’m pretty confident I did it wrong.

My networking knowledge is very basic. Can anyone help me configure my pfSense so that my L10s on one subnet can be discovered by Home Assistant (technically, by the Xiaomi Miot Auto integration in Home Assistant) on the other subnet?