I recently reinstalled Windows 10 and Ubuntu 21.10 (in that order) in EFI mode. I had assumed that grub was superfluous even in that situation: I figured the BIOS would see that there's an EFI partition with several operating systems and let me choose one.

Well, apparently it doesn't work that way. The BIOS still just lets me pick a disk (or flash memory, pxe, ...). And then grub takes over.

Hilariously, Ubuntu did not automatically set up an entry for the Windows 10 install (something that had always worked for legacy setups). Had to do it by hand. Really not something I would have wanted to spend time on.