I am rather infuriated that it's impossible to disable IPv4 on my devices, so does that make us even?

Yes I believe so!

I recently purchased a brand-new LaserJet printer, and since it needs nothing to do with the Internet or a WAN outside my home, I thought it'd be great to simply disable IPv4 and stop doing the DHCP dance.

Well it immediately fell off the net completely. I couldn't figure out how to expose its IPv6 address or contact its management interface.

Hypothetically, Bonjour and mDNS should make this a no-brainer. Hypothetically, disabling IPv4 shouldn't even prevent it from connecting to the Internet. But I was ultimately forced to factory-reset it.

IPv6-only LAN makes a lot of sense for most people, and perhaps reduces attack surface a little. If you have the means, I highly recommend setting it up!