One way is to apply for Bulgarian citizenship by investment. The problem is that, as per the amended law of March 2021, you are required to obtain preliminary approval for your investment intentions from the Bulgarian Investment Agency. And this approval is not an easy thing to do. The other way around is to contact Posolstvo.eu (in Bulgarian Posolstvo Embassy) for assistance as they will assist you with such letter from the relevant ministry.
What investment requirement would I have to meet in order to obtain a special government letter to visit Bulgaria?
How can non-EU investors get the necessary permissions to visit Bulgaria to explore investment immigration opportunities? I've heard one needs a special letter from the ministry. Would I be able to get all such permissions online?