Mine 21e8, or don't, whatever.
Run node minerid to configure your Miner ID and default payout settings
Use this TX template with a certain output
<sha256 hash of something you want PoW for> <21e8 + target string in hex> OP_SIZE OP_4 OP_PICK OP_SHA256 OP_SWAP OP_SPLIT OP_DROP OP_EQUALVERIFY OP_DROP OP_CHECKSIG
Here's a jsfiddle to get you started: https://jsfiddle.net/fkt7qb15/
You can listen for 21e8 jobs to mine here if you're fast enough
And you can see all previous jobs here if you're too slow
You can mine jobs from the cli. Just do this and follow the prompts
git clone https://github.com/deanmlittle/21e8miner.git
cd 21e8miner
npm i
node index
If you don't know how to get p2pkh addresses, use https://polynym.io
Check the blockchain.