I don't see TeXPad mentioned anywhere. An iOS LaTeX environment, featured here a few years ago: https://www.texpad.com/blog/latex-ported-to-ipad https://www.texpad.com/ios
But, unlike its MacOS version, on iOS it’s not as very good. For example, there is no multitasking support on iPad. The package managing relies on installing pre-defined “bundles”, which don’t tell what packages are included. On the Mac version of Texpad, we can choose between its own compiler or an external one like tex live. But on iOS, the former seems to be the only option.