A better solution (than Shamir secret sharing) are threshold signatures.

The difference is that with Shamir you have to reconstruct the private key in one place before you can sign. With threshold signatures multiple servers can collaboratively sign without ever reconstructing the private key in a single place.

For chains like Solana, Aptos, SUI that use ed25519 (schnorr signature), there's a pretty clean solution called FROST.

For Bitcoin and Ethereum/EVMs that use ECDSA it's a bit trickier but there's been a lot of research recently, so there are solutions.