This to me seems more like a logical separation than anything technical.
I use GitHub and always squash commits before merging a PR. This keeps the commit log clean and also has the side effect that you have the PR number in the merge commit.
Having said that I also suggest keeping PRs small. If you are going to reformat a code base, make that a separate commit. Updating a library, separate commit. Adding a library you need for a new feature: create a PR for the library update, base your implementation off that branch and rebase against main when the first PR is merged.
I use GitHub and always squash commits before merging a PR. This keeps the commit log clean and also has the side effect that you have the PR number in the merge commit.
Having said that I also suggest keeping PRs small. If you are going to reformat a code base, make that a separate commit. Updating a library, separate commit. Adding a library you need for a new feature: create a PR for the library update, base your implementation off that branch and rebase against main when the first PR is merged.