as @notcastey said:
Edit with Nano or emacs (you need to install it before to use it) (apt install emacs)
And then change the 8888 with 8090 to restore the port (CTRL+X and CTRL+C to exit):
Thank you for your response.
I installed Cyberpanel on Ubuntu 20.4 minimal on GCP but the problem remained.
Followed the next steps found on another discussion to solve:
apt remove dovecot-core dovecot-mysql dovecot-pop3d dovecot-imapd