I gave that a go (again!) and wasted 2 hours trying to get any kind of touch to work. It seems like the libinput subsystem for X11 required udev and all its magic to properly autodetect touch or other pointy devices. info-beamer’s operating system doesn’t use udev but mdev from busybox. It seems very difficult to get that to interact properly. I don’t see touch working reliably with any kind of “plug and play” installation method at the moment.
Result: Touch support within the browser package is not a feature info-beamer offers in the foreseeable future.