The Steam Deck will format the microSD of your choice into the Linux-based format, EXT4, so long as you use any compatible SD, SDXC, or SDHC microSD card, you're good to go.

Backstory Ok I'm going to be formatting the two 5Tb partitions and I'm going to use ext4 this time as it better supports large file systems. I'm going to be storing mainly photos and I know there ...

If you need to add an external drive to your Linux system, you might need to format it. If you want to learn how to do that process from the command line, here's your chance.