Seed for bitcoin-core qt I have a bitcoin core -qt Wallet (on linux). Tell me, can I encrypt it?
 For example, there is the electrum wallet!
It has words for deciphering.
For example, i installed the electrum and the  phrase was generated.
"I'm a fan of the  https://bitcoin.stackexchange.com"
Knowing this phrase you can install electrum on any computer,  and when you enter this phrase you get access to your balance and btc.
But what about bitcoin-core-qt? because it is characterized by the fact that the it must download all the transaction history after installing.(~200gb).
Is there such a "magic phrase:" for this wallet bitcoin-qt?
This is a very useful option if you have lost access to the server or host where you hadthis wallet
You can export private keys from Electrum and BitcoinCore. You can export private keys from Electrum as "words" format (There's a website to convert it to private key(s): https://iancoleman.github.io/bip39/), while Core doesn't have this feature. See the steps in question Using dumpprivkey to make a paper backup to use dumpprivkey in Core to export the private key.