Of course it's the first thing I did is too check that I send from btc wallet with bitcoin.
So it's from the default wallet then,
and you restored it using the default derivation path for legacy 1st account in Electrum as well, with zero balance.
You can now safely assume that the "
fake balance" is blockchain.com's fault.
You can contact their support for clarification, though.
FYI: If the selected wallet actually have a balance, the error will show as "
Not enough funds. Use maximum" instead of "
Insufficient funds".