Dappnode is a web3 Operative System that empowers non-technical users to run Ethereum validators in their own hardware, contributing greatly to decentralizing the network and seeding Home Operators across the world. Dappnode’s principles are self-sovereignty, decentralization and privacy, so by design we cannot know how many validators are running on Dappnode. Nevertheless, by default, Dappnode's consensus clients include the graffiti "validated_from_DAppNode," allowing users to opt in or out of this self-reporting when publishing a block to the chain. While Dappnode respects privacy and doesn’t track user data, EthSeer reports that over 3,000 validators are currently self-reporting as using Dappnode.
https://ethseer.io/entity/dappnode?network=mainnet