i think the pre-defined fuses for the AVR64DD28 leave the UPDI pin in gpio mode and set the MVIO register bit in a reserved configuration, neither yes or no. I could change the reset pin mode and bod level so that works.
perused fuses.py and didn't see an updi pin associated with the dxcore. Also, MVIO seems to be associated with DB series only.
Selected fuses:
-------------------------
[fuse0 / wdtcfg = 0x00]
[fuse1 / bodcfg = 0x00]
[fuse2 / osccfg = 0x00]
[fuse4 / tcd0cfg = 0x00]
[fuse5 / syscfg0 = 0xC9]
[fuse6 / syscfg1 = 0x06]
[fuse7 / codesize = 0x00]
[fuse8 / bootsize = 0x00]
[lock / lockbit = 0x5CC5C55C]
-------------------------
threw these into microchip studio and compared them against the datasheet.
toolchain info ...
PLATFORM: Atmel megaAVR (1.9.0) > AVR64DD28
HARDWARE: AVR64DD28 24MHz, 8KB RAM, 64KB Flash
PACKAGES:
- framework-arduino-megaavr-dxcore @ 1.5.6
- tool-avrdude @ 1.70100.0 (7.1.0)
- toolchain-atmelavr @ 3.70300.220127 (7.3.0)