Browsing the site from Firefix fails (Issue), from Chromium it printed curl https://sh.rustup.rs -sSf | sh.
I added -x to sh and ran it on my system (x86_64 kernel, mixed, mostly 32-bit userland from Debian mostly jessie) from a separate user.
It has installed itself and worked well.
Additional target works.
Additional toolchains and cargo not tested.
Nitpick: rustup target list show non-installable on stable targets like mips-unknown-linux-musl
Default installation weights 304M. With additional musl target - 346M.
Shall I also test using rustup.rs atop of existing multirust installation?