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All of these are Vdd=1.8V parts, the STM32F429 is able to run down to 1.7V so that shouldn’t be a problem. It might however make interfacing with the modem awkward since that is designed to run straight off a 4.2V Li-Ion/LiPo battery and the I/O interfaces are 2.8V CMOS levels.
Looks like only the GL865 has 2.8V levels, GL865 v3 has 1.8V levels. I was going to use that one eventually anyways the v3 version has a QFN footprint. The M66 only comes as a 2.8V version, but given how cheap it is I’m just going to deal with that.