You could also set up the lightning protocol to allow external funding. E.g:

* Perform initial setup with channel partner

* Setup transaction depends on an input that doesn't exist yet

* Once everything is ready, send a taproot address to someone who was about to pay me anyway

* that UTXO now becomes the input to the channel, and therefore it is open

Not an op-code expert so can't say for sure if it's possible, might require sighash noinput.