For most starting out it's editors in playstore, There are editors for different langugages, I started with the pydroid editor. There you can write code and hit compile to show the output. As traversing menus by hand gets quite hard, the next approach is probably to learn termux and terminal as everything is keyboard driven.

I have tried jupyternotebooks, vscode on browser but the small screen is the real blocker and you can barely see the editing field.

I use termux for everything now, for websites I just open a localhost port and see it in my browser or do live reload in spare phone. Video and images are also redirected by the termux to respective apps.