Can anyone else fund my channel? For example, Bob and Alice have a channel that is 0.001BTC, can Jack transfer 0.0001 coins to Bob and Alice's channel outside the LN and thus increase the channel volume to 0.0011?
As far as I know, this isn't possible.
The idea is if someone has to send me BTC he can directly fund my channel.
A way around this is to use a custodial wallet. This this morning I asked someone to pay to a Bech32-address that goes straight into my BlueWallet LN balance, and by creating a new LN wallet each time, I can use different addresses for this.
Custodial isn't perfect, but for small amounts I don't mind.