On digital ocean you get a very limited set of boot options. You can't provide them your own installer, boot image, kernel, iso, or any of that jazz.

You also don't get a pre-boot console.

For linux, they don't even let you provide your own kernel in userland or the like, so there's actually no way to install a BSD from a linux shim on DO.

FreeBSD on DO is the only way to get an instance that is capable of booting anything non-linux, so it's necessary to start from freebsd.

Edit: It looks like the kernel limitation has been lifted for some linux instances too. See: https://www.digitalocean.com/community/tutorials/how-to-upda...