Rpi4 error: no override and no default toolchain set

[niksfirefly]

On Raspberry PI4 with Raspbian i get
error: no override and no default toolchain set
no matter what rust version installed

I got asdf installed system wide on /opt/asdf
with
ASDF_DATA_DIR=/opt/asdf
ASDF_DIR=/opt/asdf
and
rust 1.46.0
on .tool-versions

what can i do more to run rust?

[jspraul]

This happened after I failed to follow the asdf rust plugin README's instruction:

After you have installed rust, do NOT follow the directions it outputs to update your PATH -- asdf's shim will handle that for you!

The install outputs:

Rust is installed now. Great!

To get started you need Cargo's bin directory 
(/Users/user/.asdf/installs/rust/stable/bin) in your PATH
environment variable. This has not been done automatically.

To configure your current shell, run:
source /Users/user/.asdf/installs/rust/stable/env

After copying + running the given source command I got the error mentioned (error: no override and no default toolchain set).