Dating men who are in an open relationship?

For context, I am a black female (33) who is never married or have kids. Went out on a date with a nice guy that I thought he could be the one. But near the end, he confessed to me that he is currently in an open relationship and his partner is well aware of it. I didn't get to talk more about the whole open relationship with him because it was near the end of our date. Now, I am having a very conflicting thought about if I should keep going out with him or not. I have never been in an open relationship before but I have heard of it. Does anyone here have been in an open relationship before? Is it a red flag? Do you think it could still work out in the long term?