There's iSH for iOS, that tries to be similar to Termux. I don't know if it has feature parity or not since I've only heard about it, not used it myself, but I don't want to say this area is an Android-only feature.
Does seem quite preliminary though, yet.
Point remains that availability of similar capabilities to Termux does not really yet exist on iOS.
I do appreciate knowing about the tool thogh, thanks.