Can't run rpi-update

I’m trying to output the video to a 3.5" screen and the instructions say I need to execute

sudo REPO_URI= rpi-update

I’ve successfully added this screen for my other pis, but with OSMC I get

sudo: rpi-update: command not found.

I’ve ran both sudo apt-get update and upgrade.
I cannot skip this step unfortunately it seems. Later in the instructions I’m supposed to edit /usr/share/X11/xorg.conf.d/99-fbturbo.conf, but it doesn’t exist. I assumed it was because I haven’t run rpi-update yet. I’ve tried skipping these steps but the screen doesn’t output.

I need some guidance. What am I doing wrong?

You are going to have several issues here. First,OSMC blocks rpi-update so that we have some control of the firmware. This is so that new firmwares are only installed after the team has been able to ensure that function and performance are not negatively effected for our users.
Second, OSMC does not use X11 and you are going to have complications if you try to install it and make it work.
I’m not sure what instructions you are trying to follow but, they are not for installation on OSMC specifically. It is unfortunate but installing a touchscreen on an Rpi that uses a Kodi-centric distro like OSMC or Openelec is no simple matter. In all honesty, it likely hasn’t even been done enough times for any good tutorials to be written for accomplishing it. Here’s a Kodi thread that may give you a bit more understanding and includes a few links…

The short answer is: all of it

OSMC is a Debian distro

RPI-Update is for raspbian

and as ActionA said even if you did succeed in installing it its probly gonna break the platform

I can’t seem to come up with any Pi projects that are possible… this sucks.