Can we install Clear Linux from an existing installed Linux e.g Arch Linux on a blank partition through chroot ?
If you can get
swupd working, you can point it to any mount-point and it should write the root partition from any OS.
You can build it from source: https://github.com/clearlinux/swupd-client.
Another trick to get swupd if you have docker on your existing OS, would be to use the clearlinux image from DockerHub and passthrough a volume to download Clear Linux content to.
clr-boot-manager can do the rest.
If you do this, let us know how it goes. I’d be curious.
You might have some luck with mkosi as well since in theory this will install content and the tool is available on other distros.