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Crypto Indizes

https://www.bitpanda.com/de/preise/crypto-index/bci5

1,99 % every Buying/Selling in this ivestmeht

Furthermore, I think that Bitpanda will report everything to the German tax authorities in the future.
Are there such crypto products where Bitcoin or Ethereum is offered somewhere, e.g. as a diversified investment?
Binance allows you to buy basic indexes at no cost.
But you can easily build your own index based portfolio, with properly weighted components, through an api or just manually. Check https://cci30.com/, the components are listed here: https://cci30.com/ajax/getQuarterlyComponentHistoryProd.php and their weights here: https://cci30.com/ajax/getMonthlyPropWeightHistoryProd.php