This just sounds like a different version of mycoprotein or quorn.

Not to discount their efforts, the more like them the better.

This is amazing - is there a catch? What's up with the "Finnish investors only" rule?

Some countries have mechanisms to allow restricted investment by, essentially, retail investors, without being a full public company. These are usually idiosyncratic enough that they're country-scoped and not open to foreign investors.

The company does have at least some non-retail foreign investment.

Seriously anxious investors can usually set up a local operation to channel funds and build networks.