If you don't know how to obtain a BTC #Liquid address, check this out, it's a cool phone wallet you install in your phone..
Otherwise check 
Or visit their nostr profile.. @Blockstream
SideSwap - Settlement infrastructure of the Liquid Network
The most convenient way to hold, send, receive and swap assets on the Liquid Network, a bitcoin sidechain built for securities issuance and trading.
Blockstream Help Center
How do I get Liquid Bitcoin (LBTC)?
Liquid Bitcoin (LBTC) are transferred to the Liquid sidechain from the Bitcoin mainchain through a process known as a peg-in (also known as bridgin...