Whether staking ETH on an exchange like Kraken is considered an exchange of tokens and triggers a taxable event depends on your jurisdiction. You can check out Crypto Tax UK: Expert Guide 2025.
If you want your ETH → ETH2 transaction to be tax-free in Koinly, you can manually set the worth of the received ETH2 to match the cost basis of the sold ETH (as shown in the screenshot). This effectively nullifies any gain.
That said, we are not tax advisors, and we strongly recommend speaking with a professional accountant to confirm how your staking transactions should be reported under UK tax laws.