Mining has become a business and it’s growing. It has daily expenses and for that miners need to sell their BTC to cover up electricity bill and other cost if exists. But is there any known miner who has not sold their BTC for a single time who is mining for a long time now? We know there are addresses which haven’t moved their BTC for a long time. Is any miner included in the list?
Is there any way to know this? Unless the miner signs a message from the address he was using for bitcoin mining - no! There are a lot of "frozen" bitcoin addresses and most of them are just dead ones. It's impossible to select unused ones from dead ones because every address is considered dead that has been filled 5 and more years ago and hasn't moved a single satoshi from it.
Btw there is one database done by Loycev, if anyone wants to manually check addresses and all the traces associated with them:
List of all Bitcoin addresses with a balance