OpenSSL

Generate a Self-Signed Certificate

openssl req \
-newkey rsa:2048 -nodes -keyout domain.key \
-x509 -days 365 -out domain.crt

Source: https://www.digitalocean.com/community/tutorials/openssl-essentials-working-with-ssl-certificates-private-keys-and-csrs

See also

• https://wiki.archlinux.org/title/OpenSSL
• https://www.openssl.org/