Strange boot folder transformation in ubuntu 18.10!?

[Paeryn]

Regarding your first sentence, I certainly understood Linux mounts based on your last sentence, i.e. devices are usually mounted to empty directories, hence the confusion. The fact that the /boot folder on partition 2 is not empty to start with should have been emphasized early on in this discussion - because that begs the question as to why it's pre-populated with files and other sub-folders if it's sole purpose is to be replaced by another mount point.

feelslikeautumn quite clearly said it wasn't empty in their second post in this thread.

Due to how the raspi3 images were built there are files in /boot/firmware before it is mounted. This is a bug (one that I also pointed out, but again ignored).

It may be that the files were meant to be copied whilst a partition was mounted, if for any reason it wasn't mounted at that time then the files will have been copied into the directory instead.

[gilius]

In hindsight we can now interpret feelslikeautumn's statement, but without the context of what we were discussing - namely partition 1 being mounted to /boot/firmware - his isolated statement did not make any sense. And it doesn't seem like you know for sure why /boot and /boot/firmware has stuff inside it already - just guessing. Is it a bug? Again, I plan to compare more distros over the weekend to try to get a more deeper understanding of what's happening. Flash-Kernel vs. U-boot vs. Grub, including a supposed EFI involvement has yet to be demystified.

[Paeryn]

I don't know for sure because I have never used Ubuntu on my RPi. Without looking in to it can only guess as to what is happening based on what has been said.