Following the infamous DAO hack of 2016, Ethereum split into two blockchains: Ethereum, the second-largest cryptocurrency by market capitalization, and Ethereum Classic. The newly created chain is the currently used Ethereum network, and the hacked chain continues to operate as Ethereum Classic.
And, as a shift to PoS would effectively make Ethereum miners obsolete, all eyes are now on Ethereum Classic (which will continue to operate using more traditional mining mechanisms).
Antpool, for example, recently announced a $10 million investment to back quality projects built on Ethereum Classic (ETC). Backed by mining hardware manufacturer Bitmain, Antpool is the third-largest Bitcoin mining pool and 14th-largest Ethereum mining pool, according to data from btc.com.