Although I’m currently a heavy Vim user, I still think that VS Code is one of the best editors available - and it’s open-source and free to use.
Traversy Media published a neat YouTube video yesterday: VSCode In The Cloud - Setup a Remote Dev Environment. It shows how to install an instance of the VS Code editor on a VPS server.
You can then access VS Code with your browser. This is quite useful for coding on a Chromebook, for example.
The (open-source) repository behind this magic is codercom/code-server.
You can either sign up for their IDE (free for personal use) or host the repo on your own (what Traversy Media shows in his video).
The instructions are straight-forward but Brad Traversy does a good job at walking you through all the steps.