GitHub's built-in branch protection rules do not allow for per-branch configuration of merge strategies.

But, you can enforce a "linear history" for specific branches. This has the effect of requiring either squash and merge or rebase and merge, disallowing traditional merge commits.

For master:

• Enable "Require linear history" in the branch protection rules for master. This will allow either squash or rebase merges, aligning with your goal of a clean history. You would then rely on team discipline to choose "rebase and merge".

For develop:

• Enable "Require linear history" for develop as well. This forces either squash or rebase.

This only disallows traditional merge commits. You'd still need to trust your team to select the correct option when merging into master.