If you want decentralized without hosting your own servers, you can store data on a public blockchain. Each interaction pays a small amount of gas that grants them hosting indefinitely. Protocols are a progression from platforms since they can be ownerless. Blockchains enable protocols by acting as a general purpose database.

This is what I'm doing with https://nonphysical.systems

It's still under construction so it's on Polygon mumbai testnet therefore gas is free. The source is linked in the first message board.