You can roll for an ULA prefix once, note it down in some text files and then assign your pets to <prefix>::1, <prefix>::2, <prefix>::3, etc. mDNS might also h

You can roll for an ULA prefix once, note it down in some text files and then assign your pets to <prefix>::1, <prefix>::2, <prefix>::3, etc. mDNS might also help, I haven't tried that approach.