A bit late, but this one is easy!
This is the best one but sometimes it's too long and messes up results:
"All trademarks, copyrights, comments, and images on this page are owned by and are the responsibility of their respective parties."
Can try these ones:
"powered by vichan"
Another approach is a bit backwards, you find generals and then go back to their homes:
If you want liveboard:
"meguca is licensed under the GNU Affero General Public License"
You can also ask your frens!
There was a big PDF or something that some guy reviewed all the imageboards and spinoffs he could find like back in 2015-ish. If they still up and running since then, they must be pretty robust community, but you'd have to find that PDF or word doc or whatever it was!!