Crypto taxes in Germany by blockchain

Yes. The Income Tax Act and the finance ministry's letter speak of crypto assets, not of chains: a swap is a swap, whether on Solana, Ethereum or another chain (paragraph 54). The same one-year holding period, the same €1,000 limit and the same €256 limit for income apply. The only difference is what a chain's protocols do technically, and so what a transaction is for tax.

No. The exemption limit (Freigrenze) applies to all private sales of a year together, across all chains, wallets and exchanges. Only the order is worked out separately: if you bought the same coin several times, then in each wallet the one bought first counts as sold first (paragraphs 61 and 62).

You pay the fee in the chain's coin: in SOL on Solana, as gas in ETH on Ethereum. That coin leaves your wallet, which makes it a small sale. On a taxable swap, the fee counts as deductible expenses (Werbungskosten) and reduces the gain (paragraphs 57 and 59); on a transfer between your own wallets it doesn't count as a cost.

If the same token arrives in your own wallet on the other chain, on TaxMaxi's reading that isn't a sale: it keeps its purchase date and cost basis. If a different token arrives, it's a swap. There's no explicit rule on this; more under Crypto bridges and taxes.

In the app, Solana, Ethereum, Base, Arbitrum, Optimism, Polygon and BNB Chain: an address you've used on several EVM chains is read by TaxMaxi on each of them. So far, Solana and Ethereum have their own pages with protocols, a real transaction and an example in euros.