LNURL works by using HTTP requests to do things like:
LNURLw: ask a server to pay an invoice (server tells you that you must send an invoice of min <= x <= max sats, you send one, payment made)
LNURLp: ask a server for an invoice (server tells you that you can request an invoice of min <= x <= max sats, you request, you get an invoice to pay)
LNURLauth: sign a message the server sent for authentication (server tells you to sign a message, and your client signs a message with the domain of the service, and the data provided)
Is there a existing/planned way to add funds to lightning channels after they've already been opened? E.g. have two receive addresses on a channel to add funds to one side or the other?
You cannot have "receive" addresses for both sides of the channels.
There are two ways to get more sats on a channel:
Submarine swaps: Pay someone on chain to send sats off chain. Has sometimes 1% fees due to the high demand of these services. Does not increase the capacity of the channel and requires you to have inbound which will be converted into outbound when you receive the swap payment.
Splicing: Implementation in progress. This means closing and reopening a channel with the same balances plus the spliced in funds. Capacity changes.
I'm aware of submarine swaps. My question intended to ask how to add funds on-chain to an existing channel rather than need to open a new channel. For example, say I have a channel open to my favorite coffee shop with 1Msats and after a few months I have 3500 sats left on the channel. Rather than closing and reopening the channels I'd like to send more onchain funds to my side of the channel rather than paying for three onchain transactions: 1) close the 3500 sat channel, 2) send funds to my lightning wallet, 3) open a new channel to the coffee shop.
Is there a way to make the original channel a taproot address so child address deposits show up in the parent balance, or am I misunderstanding taproot?
It is not possible to add any funds to an already open channel.
Channels don't work as you think -- it's a single UTXO that has a constantly changing force close TX.
Adding more UTXOs would lead to loss of funds and be really hard to integrate it into the protocol. If you send sats to a channel multisig unless your partner cooperates those sats are gone.
bostool for swaps and I might make one eventually.