[not my answer!][1] But since this was asked 4 days ago and I was curious too about this, here's what I found.

> Miners mine empty blocks during the time it takes them to download new transactions, which is circa 100ms. If they happen to find a valid block during that time, they broadcast it to the network, collecting base reward.

They won't get transactions fees but will still get a block reward.

  [1]: https://www.reddit.com/r/ethereum/comments/oygsv5/comment/h7u8kme/?utm_source=share&utm_medium=web2x&context=3