I've yet to study more about sidechains such as Liquid, so I can't say whether those off-chain solutions are trustless, but I'm relatively confident they are; otherwise nobody would use them.
You definitely need to trust the federation that controls peg-outs [1]. From the whitepaper [2]:
> As a sidechain, Liquid supports transfers of bitcoins into and out of the system by means
of a cryptographic peg. Bitcoin pegged into Liquid is referred to as Liquid Bitcoin or LBTC. The forward progress of the Liquid ledger and custody of the underlying bitcoin are
controlled by a federation, and remain secure as long as over 2/3 of its members are honest.
[1]
https://help.blockstream.com/hc/en-us/articles/900001551783-What-is-a-Liquid-peg-out-[2]
https://blockstream.com/assets/downloads/pdf/liquid-whitepaper.pdf