> In many places there were no race requirements for suffrage and if you were a "free negro" who met the other then-qualifications (male, land owner, etc.) then you could vote

Assuming the local official followed the law as written (hint: they didn't). Much like they would have for most of the post-Civil War, pre-Civil Rights Act era, they would have simply come up with an excuse not to let the rare free blacks who met the legal qualifications vote.