The biggest change with the Thanos update is the appearance of a brand new algorithm for Ethereum Classic mining. Indeed, ETC has created a variant of the current algorithm to calibrate the epoch duration. This name is etchash and it will take the place of ethash algorithm. This algorithm change makes you use new versions of mining softwares because they have to be compliant with the new hard fork. The current versions of certain mining softwares cannot be able to mine Ethereum Classic after the Thanos update. So, you must upgrade or install a compatible version to mine ETC.
Another change with this fork is the non-support of NiceHash. As you may know, NiceHash is the biggest marketplace in the sector of rental mining. Thanks to their service, you can rent hashrate to mine any cryptocurrencies. However, NiceHash has decided to not support this update and so you will not be able to rent hash for Ethereum Classic after Thanos fork.