Found argument '--channel' which wasn't expected, or isn't valid in this context

Possibly related to bug #1809259.

I'm using this yaml https://pastebin.com/Gz507Ak7

But with "rust-channel: nightly" in the part.

I get:-

Pulling ncspot
Cloning into '/root/parts/ncspot/src'...
remote: Enumerating objects: 305, done.
remote: Counting objects: 100% (305/305), done.
remote: Compressing objects: 100% (102/102), done.
remote: Total 1138 (delta 218), reused 284 (delta 203), pack-reused 833
Receiving objects: 100% (1138/1138), 491.96 KiB | 1.34 MiB/s, done.
Resolving deltas: 100% (769/769), done.
Downloading 'rustup.sh'[==========================================================================================================================================================] 100%
/root/.cargo/rustup.sh -y --no-modify-path --channel nightly
info: downloading installer
error: Found argument '--channel' which wasn't expected, or isn't valid in this context