That is correct, the Mayfly v1.0 and 1.1 boards do not have a separate external power input for 4v to 12v sources like the v0.5b boards. This is because the main voltage regulator on the v0.5b board that accepted that wide range of voltage was discontinued by the manufacturer, and the new voltage regulator doesn’t accept that high of an input voltage. However the tradeoff is that the new regulators have double the current output (1 Amp instead of 500 mA).
To power a Mayfly v1.0 or v1.1 board from a 12v battery, I’d suggest a 12v-to-5v power adapter with a USB-C plug on the end, and just plug it into the Mayfly’s USB port, and preferably one with a low quiescent power draw so that it doesn’t waste too much power on the dropdown. I think a few people on the forum here have recently mentioned adapters that they’ve had either good or bad results with. Something like this might work, but I haven’t test this exact model so performance results with a Mayfly aren’t guaranteed. You should also turn off the dip switch (after programming and when you’re ready for deployment) for the USB LED because it’ll save several mA of current for the LED and about 10mA of current for the CP2102 USB adapter chip that is powered anytime the Mayfly v1.0 or v1.1 is powered by a USB cable.
The other improvement of the new Mayfly boards when paired with the new sim7080 LTE cell boards is that these cell boards no longer require a direct connection to a 3.7v lipo battery like the Digi LTE boards did with the custom adapter board. Those older setups were harder to power from a 12v battery because you still needed to provide a separate Lipo battery for powering the LTE board. Now with the new sim7080 LTE cell boards, everything can be powered from just the 5v USB connector with no external lipo necessary.