Can I sir ask you for what purpose you want SFTP,
If you want to upload, download, and edit user web files then you can do it by inbuilt file manger in Hestia or you can use filezilla etc, I provide a video for that too
normally steps for ftp and SFTP almost similar and you says sir that ftp is working, so SFTP is working too, maybe then required ports in not enable in Oracle for that check above video too.
If you want SFTP for as backup then you can read official document in Hestia website. I use rclone (previously I use backblaze) for backup so for SFTP please follow official document steps.
If you want to upload, download files in Linux web server, then there is many videos for that you just search it on YouTube. I use mobaxtrem instead of putty so I get ssh, ftp, SFTP in same place for Linux web server I didn’t need to setup anything more in this ssh client, you can use it too if you want.
But again it’s all depends for what purpose you want SFTP.
I hope it helped you sir.