Can not sign for this input with the key `03...` about bitcoinjs-lib

[junderw]

The bc1qdlxcmcncy059gw0my604y35s5257mxua6ttlje output is at index: 1, but you're using index: 0,...

I don't understand what you're talking about. Your input is clearly pointing to a different UTXO.

[junderw]

The error is pretty clear.

It can’t sign for that input with that pubkey because that pubkey is unrelated to that input.

[bormisov1]

The error is pretty clear.

It can’t sign for that input with that pubkey because that pubkey is unrelated to that input.

Sorry, what do you mean unrelated? This txn has bc1qdlxcmcncy059gw0my604y35s5257mxua6ttlje as output address, which can be derrived via bitcoin.payments.p2wpkh from 03163883cf37d71960982ee74ad91168160322688a78769f9c3db9bc72ab1142a9 pubkey.
And this hex is a raw representation of referenced tx:

010000000001017a5d1fd9635a4fe15beff85a18fc32651ff07736abc24d07afa9d0d8b66c656d0000000000ffffffff02b80b0000000000001600142e212c99d59342f463726ea8f0340a48f56fde049b530000000000001600146fcd8de27823e85439fb269f524690a2a9ed9b9d02483045022100ecab202e666a63668a1b68dcd873be4d57d61e2cbdd8f39b895e70d384b3e143022031ca826e45e944f38d4c9e95dc23ecf97035ed4b73b094feee84f057e0c1e721012103163883cf37d71960982ee74ad91168160322688a78769f9c3db9bc72ab1142a900000000

[bormisov1]

The bc1qdlxcmcncy059gw0my604y35s5257mxua6ttlje output is at index: 1, but you're using index: 0,...

I don't understand what you're talking about. Your input is clearly pointing to a different UTXO.

Oh sorry, that was so stupid of me. Indeed this index: 0 caused the issue, and the code worked by coincidence when I had output mint index match an index at which this output would go in a new transaction. Sorry for wasting your time.

At least might be a hint for somebody as heedless as me in future... Thank you for your help and for this repository!