KDBX 4.x format (Keepass >=2.36) is not supported by keepass2john yet, so there is no known way to extract the hash and crack it.
This tool is a quick and dirty patch for the current situation. It tries to bruteforce the passphrase testing a provided wordlist directly against the db file.
- keepassxc-cli
./keepass4brute.sh <kdbx-file> <wordlist>JohnTheRipper related code comments and issue: