When creating users, I always manually pick a UID/GID, generally starting at 2000, which, from experience, is the lowest number that does not conflict with any system range on any UNIX-like OS.
I start my manual picks at 3000 to avoid conflicts with users created by people like you. (I'm not only making a joke, I really do. My siblings are people like you, too.)
I appreciate your anti-collision efforts. ;)
Why do you manually pick user UID/GIDs?
So they are the same everywhere.
Cool, just curious...why do you want them to be the same everywhere?
NFS, and also just sneakernet. It means you don't have to worry about formatting large external disks with something weird like exFAT.
NFS?
Or any way of moving files around that doesn't translate UIDs or where translating UIDs is more work; ex. rsync will default to trying to match by user name, but I'm pretty sure tar won't always