What about using a GitHub Action? I think I found something at https://github.com/marketplace/actions/rust-grcov which uses grcov under the hood.

Thanks for the feedback! Yeah, it looks promising. We also want to have something that works locally, and we want to merge it with the test suite runs, but I'm sure we can get it working.

In that case it may be possible to come up with something custom. cargo has built-in support for extending its functionality.

Yeah. I just hope tarpaulin will prove itself as the easy solution.