And, since we don’t own or use any Haier appliances, we aren’t subject to their TOS.

Most people who “self host” things are still doing it on a server somewhere outside their home. Could be a VPS, a cloud instance, colocated bare metal, …

I used Mattermost for a community project, but had trouble getting people to install/use/learn yet another client.

It’s a legal complaint. Someone is going to get fined, likely thousands of dollars, if the complaint is substantiated. I strongly suspect a human will be reading the whole thing more than once, before proceeding to gather much more info.