Stuck at old dependencies

I have 2 sites, jarnocv and paintdotnet.
jarnocv is relatively new and builds go just fine.
paintdotnet on the other hand is an old site that I’ve switched over to the new 20.04 build image and for some reason it loads a dependencies from somewhere and installs node 10, ruby 2.6 and go 1.12 on every build.
Both sites have the same 2 HUGO variables set with nothing else.
No package.json or netlify.toml.

Welcome to the forums @Zagna

As mentioned in Manage Build Dependencies

We pin the site to that version so your builds won’t change even if the build image’s defaults change.

You can set the GO_VERSION to the value of whichever version is required by the build process for your site as well as a the HUGO_VERSION environment variable.

That would explain it.
I might then just delete the site and recreate it.