Chainlist.org

Linea Sepolia Testnet is listed on the official ethereum-lists/chains repository that is pulled by many cross-chain projects like chainlist.org, thirdweb, and Cookbook.dev.

You can get access to different key parameters for the Linea Testnet chains like:

1. chainId
2. RPC Endpoints
3. Native Currency settings
4. Explorer info
5. ENS info
6. Linea Network Icon

See the official repo here