bitcoind – Txindex = 1: how to recognize the blockchain with this option?

You can check the debug logs and see if you are indexing transactions:

$ tail -f ~ / .bitcoin / debug.log

You can also try to get a transaction by txid, and if you return transaction data, then the chain of blocks for the transactions has been indexed (you may have to wait for the synchronization to complete):

$ bitcoin-cli getrawtransaction {txid}