With KYC, Binance, using a credit card is the cheapest.
No KYC, Bisq, but like all P2P markets is more expensive than centralized exchanges. That., however, shouldn't be a problem if you're buying to hold long term (and if you're not, just buy at a centralized exchange then).
Binance - yes, but sepa transfers and open banking are cheaper (much) than cards.
Yeah, but at least where I live, it's become impossible to do SEPA to Binance. Only card, with the corresponding 2% penalty.
Hmm. Then Revolut is cheaper. How about crypto.com Exchange (not app)? And bitfinex?