Astar Network is a permissionless blockchain, only the most used dApps are listed in the overview.
(source: DappRadar July 26, 2022)
[Polkadot] is an open-source project led by the [Web3 Foundation]. It is a sharded protocol that connects different blockchain networks.
Parity Substrate is a framework for building custom blockchains. Substrate offers blockchain templates or you can define a unique structure and logic. Substrate implements a high level of security, making blockchain development fast, easy, and secure.