Drives encrypted with FileVault2 are supported for backup and recovery.
Similar to other use cases, disk-/volume-level recovery is available in bootable media (rescue media), and file-level recovery is available both in live OS and in bootable media.
All files are stored unencrypted in the archive (but can be encrypted with archive encryption). After recovery, APFS volumes will not have FileVault2 enabled, but it can be re-enabled in macOS after recovery.