I discovered that the files and directory that are created in (default) Termux, are not accessible to other apps on non-rooted phones.
Where is the folder that Termux defaults to?
How do I set it to use a folder / filespace that I can access through an app like ES File Explorer?
Or perhaps slightly differently, how in Termus would I change to, let's say, the default "Download" folder?
From within Termux itself, you can change the current directory to the internal storage, by means of
followed by enter. After that, create a new directory by using
Directory with a name of your choice. You'll then have a new directory in your device's internal storage, whose data you'll be able to access with any file manager.
If your device is running Android 6 or newer, you'll need to run the command
from within Termux, and then accept the request to write to the storage, in order for Termux to be able to perform directory and file creation.
termux-setup-storage command creates a new directory in your
~/ directory named
storage. This new directory contains a few symlinks to
/storage/emulated/0 listed below:
dcim -> /storage/emulated/0/DCIM downloads -> /storage/emulated/0/Download external-1 -> /storage/external_sd/Android/data/com.termux/files movies -> /storage/emulated/0/Movies music -> /storage/emulated/0/Music pictures -> /storage/emulated/0/Pictures shared -> /storage/emulated/0
Therefore, you can run the following commands to create
/storage/emulated/0/Directory described above with a little less typing now:
cd ~/storage/shared mkdir Directory
See https://wiki.termux.com/index.php?search=Storage for the newest information about using storage in Termux. https://wiki.termux.com/wiki/Termux-setup-storage is the prerequisite. Use it first. To share data see https://wiki.termux.com/wiki/Sharing_Data for more information.