Anyone including institutions can buy Bitcoin without asking government permissions.
In centralized exchanges there are two options when you want to create account, for personal or business. Without ETFs approval, as long as the current investors want to buy Bitcoin, it should be same.
Many companies invest in Bitcoin just because of the hype.
As far as I know, large institutions like public companies like Tesla or Microstrategy cannot arbitrarily buy bitcoin or any asset. They are heavily regulated by governments and regulatory agencies, which means they need to be licensed and approved by the SEC. If the SEC rejects, they can't buy bitcoin.
I also believe that without ETFs, traditional institutional investors would not be involved in bitcoin. Yes, they can invest in bitcoin without an ETF and they could have done it years ago. But have you ever wondered, why didn't they do that, why did they only start investing in bitcoin when ETFs were approved and only invest through that?