Sweden - A Mining Powerhouse, page-7

Current problem with Cobalt is shortage of supply pushing up the price. A large supplier is the DRC which has poor labor use (eg child labor) and poor mining practices. The unethical mining issues raised by the author would not be an issue with the Talga Group.
The manganese is its still in the research stage which means it could be quite some time before being a commercial option. While the price is currently low huge EV demand for it would cause at least immediate shortages and a skyrocketing price.
Once commercial if that does happen there would likely be a transition period until supply catches up with Manganese demand.
Responsibly mined Cobalt as an ethical option will probably be around for a while.
In the meantime its wait and see.