user95422: There has been a new mining pool appearing after the halving called Lubian.com cf https://www.cryptoglobe.com/latest/2020/05/new-bitcoin-mining-pool-comes-out-of-nowhere-already-5th-largest/
How does a miners say to the world who he is, and how can he prove he is the one that has mined a specific block ?

user3667: They will either reuse the address in coinbase transaction subsidy output every time they mine a block, and then publicly claim that address, or they will "tag" their name (ascii-encoded) and some metadata in an OPRETURN or the scriptSig of the coinbase transaction. 
Here's the coinbase TX from block 603526:
https://blockstream.info/tx/0eb39c3f1a6813dfe5bb9d86dd71de2593aa76f25d4f25b149c9f564eb33cd54
The script sig is
03863509fabe6d6d0f3e894118566fd52beccf2a405c060fb701171dd16d83f1fb4aa0219fa8656601000000000000002469020000535e15a74a1b00000000e6892f736c7573682f
which is ASCII for:
5  z>mm>   AVoU+lO*@\7Qmq{J !(ef$iS^'J /slush/
There's slushpool!

95422: <p>There has been a new mining pool appearing after the halving called Lubian.com cf <a href="https://www.cryptoglobe.com/latest/2020/05/new-bitcoin-mining-pool-comes-out-of-nowhere-already-5th-largest/" rel="nofollow noreferrer">https://www.cryptoglobe.com/latest/2020/05/new-bitcoin-mining-pool-comes-out-of-nowhere-already-5th-largest/</a></p>

<p>How does a miners say to the world who he is, and how can he prove he is the one that has mined a specific block ?</p>
 3667: <p>They will either reuse the address in coinbase transaction subsidy output every time they mine a block, and then publicly claim that address, or they will "tag" their name (ascii-encoded) and some metadata in an OPRETURN or the scriptSig of the coinbase transaction. </p>

<p>Here's the coinbase TX from block 603526:</p>

<p><a href="https://blockstream.info/tx/0eb39c3f1a6813dfe5bb9d86dd71de2593aa76f25d4f25b149c9f564eb33cd54" rel="nofollow noreferrer">https://blockstream.info/tx/0eb39c3f1a6813dfe5bb9d86dd71de2593aa76f25d4f25b149c9f564eb33cd54</a></p>

<p>The script sig is</p>

<p><code>03863509fabe6d6d0f3e894118566fd52beccf2a405c060fb701171dd16d83f1fb4aa0219fa8656601000000000000002469020000535e15a74a1b00000000e6892f736c7573682f</code></p>

<p>which is ASCII for:</p>

<p><code>5  z&gt;mm&gt;   AVoU+lO*@\7Qmq{J !(ef$iS^'J /slush/</code></p>

<p>There's slushpool!</p>
