There are many issues, first termux doesn’t have all packages and struggle to run some common ones. You have pages and pages of workaround in their GitHub.

Secondly, using a device on a battery to run 24/24 is nonsense, you are Puting a lot of work on the battery by constantly getting it at 100% and eventually it will break and with it your data.

Thirdly, these devices have just a usb port. Sometimes usb 2.0. What you gonna do when the 128gb is filled up ?