Ahh I had not understood that you had added cloud-utils for the purpose of growpart.
As it seems growpart is a wrapper around sfdisk, I’m not sure if it will work for my microSD card, but if I understand correctly, it has worked for yours.
fdisk had failed on old and my new microSD card. But that microSD flew away, I lost it and cannot test growpart now.
I will try with another newly bought microSD card soon and report back.
Regards,
Florian