Type of filesystem to put on USB storage, that is compatible with most OSs

The answer to your question¹ is simple:

mkfs.msdos -n 'dickEt' -I /dev/sdd1

Hoever, it comes with the following limitations:

• Maximum file size is 4GB
• Maximum partition size is 2TB

OS - File system compatibility (mini) matrix:

                   FAT  NTFS EXT[2..4] BTRFS  XFS HPFS
Amiga               x
MS-DOS, Win95, 98   x
NT, W2K, ... W10    x     x      2
MacOS               x     3      4                  x
Linux               x     x      x       x      x   x

_{Note 1: You asked for maximum OS compatibility and that's the only answer as it is compatible with most OSes as it's one of the oldest and least capable file systems. (Not ALL OSes! E.G. C64 does not support FAT!)
Note 2: Commercial Tryware if you want write capabilities.
Note 3: Commercial Software if you want write capabilities.
Note 4: Read-only}