Many newer computers now have a rudimentary bootloader integrated in the EFI. Some are actually quite nice, allowing you to browse partitions to choose which image to boot. HPs have this. You just hit a key during uefi “post” and voilà.

The functionality is present on my new Lenovo laptop, various generations of HP elite/pro books/desks, old asus mobo and newer cheap gigabyte mobo, 7th gen intel nuc.