traveller Does that mean the device isn't going to work in this areas for some hardware restrictions? Or is it just a firmware limitation that goes away with OpenWRT?
It is a limitation of the cellular modem inside of the unit. There may be other Quectel cards supported that work in those countries and allow IMEI change via AT commands.
traveller theoretical question - But how can an operator detect changing of IMEI (as opposed to SIM card being inserted into a different phone)?
I understand the generated IMEI follows some realistic pattern, like keeping the manufacturer?
I speculate here but they may very well utilize analytics that detect suspicious behaviour and trigger an alarm, like changing IMEI with the same SIM, changing IMEI too often at the same location etc.
traveller Also using Mudi+OpenWRT (that supports changing IMEI) alone is not illegal, only actual changing of the IMEI is, correct?
No of course not, it is a off-the-shelf consumer product designed for legitimate use. It just happens to be suited for these kind of modifications since the Quectel modem supports changing IMEI. Those cards support changing IMEI via special AT commands you can send to the card via serial console, and the research team behind Mudi has made a graphical UI in OpenWrt to facilitate it for the end user. If you are handy with IT DIY stuff you can theoretically use the Mudi software with any router supporting OpenWrt router if you use a mPCIe to USB adapter, and the correct Quectel card purchased off Ebay. Just try to find out what AT commands are supported in datasheets for the specific card.