Segwit has nothing to do with minimum fee rates. There is no consensus rule for a minimum feerate.
There is a policy rule for a minimum relay fee. Transactions must pay a feerate greater than or equal to the minimum relay fee configured for a node. By default, this value is 1 sat/vb, but node operators can choose to increase or decrease this value. It can also change depending on how many transactions are in a node's mempool. Transactions that do not meet the minimum relay fee are not invalid, they are simply not accepted by the node for relay to other nodes.
Miners can bypass any and all policy rules. A miner can choose to insert a transaction which pays less than their configured minimum relay fee, including transactions that pay no fee.
Given the miner of the block including this transaction, and its position in the block, it's probable that this particular transaction was created by the pool that mined that block and is being used to pay the individual miners participating in that pool.