Afaik this feature is obsolete, and currently it's not possible. Maybe in 12.1 the feature will return, not sure about it though. If Udjin lurks around here he might be able to answer.
Yep, this thing is deprecated. NOT going to be implemented in 12.1 - we had issues with figuring out the right mn winner when donations were enabled which was causing forks. Mn winner detection was refactored and improved (hopefully) in 12.1, so let's see how new winner detection is going to perform on mainnet first and then _maybe_ we can try to get this feature back (not promising anything though).