Here you will find a variety of client apps that can connect to IBM i for a variety of purposes including editing code, 5250 telnet, FTP, SFTP, SSH, etc.
The following are listed according to our personal preference :-)
- VSCode + SSHFS (article)
- RDi $886/user/yr
- MiWorkplace $27.50/user/yr
- Notepad++ for RPG