It's weird because CLN plugin didn't update its Rust edition since 0.10.2. How did you install Rust and Cargo?
I honestly don't remember install neither of them.
Do you run OpenSUSE & installed through this guide? If so, this command did it:
[1] Install dependencies, make sure you're logged into your sudoer account and not in
bitcoin.
sudo zypper install clang cargo rust tor libstdc++6-devel-gcc11
I don't know neither of the two, but isn't the error essentially saying that I have to upgrade my cargo?
The error is saying that your cargo is outdated, yes.
Leap 15.3 should be giving you Rust 1.62 and accompanying cargo version.
https://software.opensuse.org/package/rust