Cosmos: https://blog.cosmos.network/announcing-the-big-bang-stargate-testnet-a27a7b74a903
Cosmos Gaia Test-net: https://forum.cosmos.network/t/start-new-public-testnet-gaia-13007-for-test-software-upgrade-before-do-it-on-mainnet/2838https://forum.cosmos.network/t/looking-for-new-testnet-participants-made-from-mainnet-ledger/2745
https://cosmos.network/docs/cosmos-hub/join-testnet.html#starting-a-new-node
Edgeware Test-net: https://commonwealth.im/edgeware/proposal/discussion/176-final-testnet-v099-updates-and-validating-cli-commands
Celo: https://docs.celo.org/getting-started/alfajores-testnet;
https://forum.celo.org/t/the-great-celo-stake-off-baklava-testnet-launch/201;
https://forum.celo.org/t/baklava-testnet-incentivized-community-challenge/239
Polygon: https://docs.matic.network/staking/participate-in-counter-stake/;
https://blog.matic.network/matic-network-staking-update-and-becoming-a-validator/
Nucypher: https://www.nucypher.com/incentivized-testnet/; https://blog.nucypher.com/come-and-stake-it-incentivized-testnet/
Bitsong: https://btsg.community/t/validator-contest-join-to-bitsong-testnet-3-incentivized/201; https://github.com/bitsongofficial/contest/blob/master/telegram/tester-telegram-wallet-testnet.md
The Graph: https://thegraph.com/testnet
Regen: https://github.com/regen-network/testnets/; https://github.com/regen-network/testnets/tree/master/congo-1/treasure-hunt
MathChain: https://docs.mathchain.org/cn/tut_run_node/
Stargaze: https://medium.com/stargaze-protocol/stargaze-testnet-bellatrix-1-