We have updated how signing on the Lattice1 works in Q1 2022 - the new general signing framework allows us to sign transactions based on the most commonly used signing curves. This means you can theoretically sign transaction from almost all cryptocurrencies, but without wallet integrations, this is only accessible to developers.
So - if you have a coin you'd like to see added to the Lattice, reach out to the team of the wallet you're using (such as Phantom for Solana)!