Disk encryption in Ubuntu during installation - how secure is it?

Question

Encryption

Good afternoon!
When installing Ubuntu 18.04, there is an option to choose to encrypt the entire installation.
During installation, the partition "/" and "SWAP" are encrypted. /boot is not encrypted.
How secure is this encryption?
Will there be any problems with sleep mode?
Are there performance degradation issues with disk encryption like this?

Answer 1

Thermorectal cryptanalysis breaks any ciphers. This should not be forgotten. At the household level, it is quite reliable.

Answer 2

As secure as the PC is protected from physical access