ππ»Hi 1st!
Flying main cabin internationally.. I'm about 99% sure that we have access to the KLM lounge (as well any other Sky team lounge) because I am a Platinum Delta Skymiles member. A companion is allowed in for free too.
I doesn't matter whether you are flying on a Delta, KLM, or Air France flight since they are all part of the Sky team partnership.
Hope that helps.π