## How to open a channel in LND using combined funds from LND and external wallet
1. Select utxos to spend from output of `lncli listunspent`. Copy-paste involved addresses to a text file.
2. Add external addresses to the file.
3. Run recent Electrum version in watch-only mode and select "Import Bitcoin addresses or provate keys". Put the list of addresses there.
4. `lncli openchannel --psbt node_id amount_in_sats`
5. Copy the address and amount from the output and put them in Electrum's Send tab. Press Pay -> Advanced -> Finalize -> Export -> Copy to clipboard.
6. Save the PSBT to a file on the machine where LND is running (e.g. `/tmp/my.psbt`)
7. Write the file name to LND's prompt. Make sure it prints "PSBT verified by lnd"
8. Sign the PSBT on the external wallet. Copy second PSBT.
9. Complete signing on LND's side: `lncli wallet psbt finalize "Second PSBT"`
10. Copy-paste "final_tx" hex string to LND's prompt and press Enter.
More complex path, working if addresses are taproot or you know public keys of them. Use bitcoin-cli and descriptors.
Import your addresses to bitcoin core as watch-only wallet.
1. `bitcoin-cli -named createwallet wallet_name=testpsbt avoid_reuse=true descriptors=true load_on_startup=true disable_private_keys=true` where `testpsbt` is the name of the wallet used in commands below.
2. Write descriptors of your addresses. See
GitHub
bitcoin/doc/descriptors.md at master · bitcoin/bitcoin
Bitcoin Core integration/staging tree. Contribute to bitcoin/bitcoin development by creating an account on GitHub.
For example, for taproot address, use `rawtr(public_key)` where `public_key` are the 32 bytes pushed in ScriptPubKey.
For pay-to-witness-pubkey-hash, use `wpkh(public_key)` and you need to know the public key (e.g. from xpub or from the wallet).
3. Add checksums to your descriptors: `bitcoin-cli getdescriptorinfo 'rawtr(xxx)'` and copy the version of descriptor with hash tag
4. Import descriptors into the wallet: `bitcoin-cli -rpcwallet=testpsbt importdescriptors '[{ "desc": "rawtr(xxx)#yyy", "timestamp":1700000000}, { "desc": "wpkh(xxx)#yyy", "timestamp":1700000000}]'` where timestamp must be before the first UTXO you want to add to the wallet.
5. Make sure bitcoin core sees all the utxos you need: `bitcoin-cli -rpcwallet=testpsbt listunspent`
6. Use LND to open a channel as described above. Copy the `walletcreatefundedpsbt` that LND provides for bitcoin-cli and modify it like this: `bitcoin-cli -named -rpcwallet=testpsbt walletcreatefundedpsbt outputs='[{"xxx":0.01000000}]' changeAddress=<yourChangeAddress>` Make sure to put a valid change address there.
7. Other steps are the same.
