When Koinly downloads transactions from the Abstract blockchain, the incorrect ETH fees are downloaded.
Based on my research of the Abstract chain, it seems that the fee structure works differently than how it works on the Ethereum L1 or other L2s. Specifically, on the Abstract block explorer (abscan.org), the ETH fees are NOT the Transaction Fee amount listed under "Transaction Fee" as is the case with Ethereum L1 or other L2s. In order to accurately get the fees on Abstract, you need to click the "Show more details", take the "Initial" amount listed and subtract the "Refunded" amount from the "Initial" amount. Doing this calculates the correct fees.
I tested that with a handful of transactions, and that has worked in getting an accurate ETH calculation. So Koinly should update this with the Abstract blockchain in order to get accurate ETH balance calculations.
Currently, I need to manually change all the fees of the transactions that Koinly imports in order to get an accurate ETH balance calculation. This is a bug that should be fixed.