I couldn’t find any examples of executing a newfs_msdos for a FAT32 filesystem while I was working on some FPGA stuffs here at the house tonight. The fine folks in the FreeBSD Discord were able to guide me to the following in order to build a working file system on my 2GB SD Card.
# newfs_msdos -F 32 -c32 -C 2G /dev/da0
As of today’s FreeBSD 14CURRENT, you have to massage the numbers around even though this should have just worked right out of the box. I suspect the math inside of sector and cluster calculation may not be correct.