The value of the crypto assets I had acquired dropped below the purchase price, and I exchanged them for euros at a loss. Can I deduct the loss in taxation?

Yes, you can. If you generate a loss from the use of crypto assets, the Tax Administration will primarily deduct it from your capital gains. If you do not have capital gains, the loss will be deducted from your capital income. If you have no capital income or if your capital income is less than the loss to be deducted, the deduction will be carried forward to the next 5 years.