FAT32 is the usual portable filesystem.
FAT32 is the current usual but "future has been" portable
filesystem. FAT32 doesn't allocate partial blocks, so a
direct copy of some linux directory often results in a very
large loss of free space on FAT32. FAT32 limits you to
files under 4GB, and partitions under 32GB. You can
create a FAT32 filesystem with smaller allocation units,
but that probably reduces the partition size limit and
many not be supported on some devices.
When moving files between linux and other systems I generally use
archives to preserve ownership and permissions, while avoiding
small file allocation problems. The way forward is exFAT:
https://fossbytes.com/linux-5-7-microsofts-exfat-driver-code/
TL;DNR: