The best training is a solid initial foundation, and continuous development as long as the position is held.
Certifications are only as valuable as the institution issuing the certification. As a whole, there are no necessary certifications to be an effective barista. In fact, the best baristas I know scoff at the idea of any institution declaring to have "The" standard.
Non-traditional career paths are as diverse as imaginations allow. "Boring" is rarely a valid descriptor.