FAT32 is not a bad choice. It's a relatively simple filesystem that reduces the amount of stuff the UEFI has to deal with while also being understood by basical

FAT32 is not a bad choice. It's a relatively simple filesystem that reduces the amount of stuff the UEFI has to deal with while also being understood by basically any modern operating system (modern = since 2000) The only other option I'm aware of that is cross-OS would be UDF, which back then wasn't popular outside DVDs and even today people continue to ignore. Though it would have been patent free.