Microsoft’s Wolverine for the TCP stack was not available until Windows 3.11. An argument could be made that these systems are defacto air-gapped as they cannot communicate with modern networking.

I have that exact machine in my electronics “graveyard”.

Peppermint OS was my GO-TO for speed and driver support out of the box. You can also stick in a 2GB SODIMM of ram. It will only recognize 1.5GB but still 50% more ram.

A fathers day card from the dollar store. Include a gift card from the same dollar store. Put no money on the gift card.

Not 6E but the GLINet Flint 2 runs a flavour of OpenWrt 23.05.

I own the original Flint and I have been really happy with it. It’s has a “fisher price” mode for most people; but then you can also log into Luci and really tinker under the hood.