Short answer: YES.
Read more about "zero-confirmation" channels
https://docs.lightning.engineering/lightning-network-tools/pool/zero-confirmation-channels

The 0-conf channels are literally what you describe as "offline" channels.

Or how I described here running a "private" LN
https://stacker.news/items/843264

DarthCoin

Is it possible for Alice (with some bitcoin in her wallet and LDK) to create a channel with Bob (she knows Bob's credentials), sign it on her side and give to Bob on a flash drive, so he signs on his side and transmits to the network?

The reason - what if Alice can't reach Bob via internet or any way via LN channels? I suppose there should be some way for Alice to still spend her money...

I've checked PSBT and in general seems doable, but it looks like there some other communications need to happen between Alice and Bob? Who can help and describe the mechanism?

lightning

Is it possible for Alice (with some bitcoin in her wallet and LDK) to create a channel with Bob (she knows Bob's credentials), sign it on her side and give to Bob on a flash drive, so he signs on his side and transmits to the network?

The reason - what if Alice can't reach Bob via internet or any way via LN channels? I suppose there should be some way for Alice to still spend her money...

I've checked PSBT and in general seems doable, but it looks like there some other communications need to happen between Alice and Bob? Who can help and describe the mechanism?