Qatar sells some business class fares which are “unbundled” and don’t include lounge access.

I think they are called Business Lite and book into P class.

I’m not sure whether BA sell such fares for travel on Qatar metal. I think probably not.

Just as a PS, every time I go to a Qatar lounge at an outstation there is an angry business class passenger rowing with the lounge dragon about access. I think it catches a lot of people by surprise.