I want to run my node in the testnet for testing and learning purposes. Where can I find neighbours for it? Is there some kind of public list of public testnet nodes?
you can find a #testnet channel on the new IOTA Discord https://discord.gg/5spymQ, ask there and you will probably find people to connect with.
There is a #testnet channel on the IOTA Slack also, but this tchat will be closed and people are currently migrating on the Discord.
You can visit https://nodesharing.wisewolf.de/, which can automatically assign you testnet or mainnet neighbours for the Chrysalis network (IOTA 1.5, as currently live).