It is my understanding the Pantheon environment can be set up on Arch - see https://wiki.archlinux.org/title/Pantheon
Here is a guide that someone wrote - you may find it useful : https://www.debugpoint.com/2021/02/pantheon-arch-linux-install/
Having said that - the main reason distros choose a base like Ubuntu/Debian/Arch to build on is because it lets them ...
It is currently not supported to update Elementary OS between versions.
However, since it's Linux running under the hood there may be someone who releases an "update script" that accomplishes this in the future.
I experienced the same issue, which seems to be caused by the grub.cfg file not being written to /boot/efi/EFI/ubuntu/grub/grub.cfg, just to /boot/grub/grub.cfg.
What I did was:
Created a backup of /boot/efi/EFI/ubuntu/grub/grub.cfg
Copied /boot/grub/grub.cfg to /boot/efi/EFI/ubuntu/grub/grub.cfg
After rebooting I was able to select newer kernels from the ...