It looks a lot better on my Linux laptop! We're investigating.

I have found bugs on that installation guide. For example it tells you to install the certificate chain to

/etc/ssl/certs/zulip.combined-chain.crt

But nginx looks for it in

/etc/ssl/certs/zulip-combined-chain.crt

Also during your installation you download this deb file to

/root/zulip/python-django-guardian_1.3-1~zulip4_all.deb

But the script then tries to install it from

/root/python-django-guardian_1.3-1~zulip4_all.deb`

Thanks for reporting! Both of those are already fixed in the latest tarball on the website.