I have j7 max with android 8. IIRC termux should run on android 5+ maybe try to install from fdroid or search older apk versions also there is userland app that you can try.
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.
Yep, I have to thank my conditions for forcing me to learn linux stuffs. As much as I would like to I cannot recommend it to friends who are just starting out to do it as I myself spend 3+ weeks to learn vim. They get perplexd on installing termux.
Sadly, this is how things are for many of us students, I currently study bachelors in CS here in Nepal and for me and some of my friends stuck in our villages (lockdown isn't still over here yet), we have been doing C assignments using editors avalialble in the playstore.
Seeing these apps have millions of downloads, we're definitely not alone and I have seen many indian and other south asian friends do the same.
My personal setup includes a 2$ stand and A samsung J7 phone paired with a keyboard over OTG cable. Since I have been doing this for few years I have a pretty complex setup of termux, a student credit powered VM from Azure, emacs. I have managed to develop python cli apps, jupyter notebooks, even flutter development using some port forwarding hacks.