Termux on Android is truly phenomenal in its capabilities. Unfortunately, nothing even close to it exists on iOS. Termux from the App store is completely unrelated, and essentially a scam.

The iOS one is pretty much just an SSH client (and also seems like a different developer piggybacking off the name)

ish and a-Shell both give you a terminal and some sort of semblance of a Unix vm with package management.

Both good but nowhere near the termux ecosystem and integration