Ledger testnet Bitcoin connection

How do I connect my bitcoin testnet address when using a Ledger device with the extension?

You'll need to install a seperate bitcoin app on the Ledger device. This is only possible after turning on the Developer mode, in settings (top right) and then clicking the Experimental Features tab:

Then click "My ledger" in Ledger live, and allow the device to connect. Searching for "testnet" will bring up the Bitcoin test (BTC) app version 2.2.0-rc2 in this case, install that:

Switch to testnet on the Leather Extension:

And then connect to bitcoin while the Bitcoin testnet app is active on the Ledger device. After connecting you may need a bitcoin faucet, you can try this or find another one online https://coinfaucet.eu/en/btc-testnet/.