Genius!
See this thread for how to turn a MAC address in to an EUI. Obviously you need several pieces of hardware with network cards in if you need more than one, but most laptops have two (Ethernet & WiFi) and desktops have Ethernet.
Or buy a pile of Microchip 24AA025E64 - last batch end of April cost me 19.8p each for 100 - some end up on boards, most get the EUI read by the office gnome (pick me or the wife) to go on file for use as AppEUI’s (one used for an application) or for our hand built LMiC devices for DevEUI’s. I have a number of gateways that pick up the EUI from the global_config.json so I have carved off some EUI’s for them. I’ve also got the code compiled from this thread for use on private instances of TTSv3 and Chirpstack for test purposes.
If you can change your gateway EUI and really really need an official EUI, ask and ye shall receive. If you can’t change it on the gateway, the community can look at the details & help track down the owner of the errant gateway.