Keystone firmware versions M-6.0 (Multi-Coin) or newer enables the Solflare Web App (v1.29 or newer) to be used with your Keystone and sets the extension as a watch-only wallet for your Keystone Essential or Keystone Pro device.
Go to Solflare.com and click Access Wallet. Step 1
Click Keystone icon on the main page.
On your Keystone: Tap the Menu icon.
Then Tap Watch-only Wallet on your Keystone device.
Then select Solflare / Slope and tap Confirm.
Scan Keystone QR code with your computer’s camera.
Select the accounts that you are going to import then tap Continue.
Set a password for your wallet, then click Continue.
Your Keystone Hardware Wallet has now been successfully imported to Solflare!