Realized I posted about this before so here you go;

Some days ago I've found an easy peasy method to sideload a modified ad-free YouTube IPK file to all LG OLED TVs from year 2020 on (so from line CX/GX on), but I got feedback here that with C9 TVs it works too.

You need a computer with either Windows or macOS (I believe an iPad might do the job too) connected in the same network.

First we have to create a free LG webOS developer account at https://webostv.developer.lge.com/login (you can change language if it's not yours), but if you already have a normal LG account just login with it so to enable also the developer account.

Now as a one time process go to your TV and from the Content Store download the app Developer Mode (made by LG itself).

Launch it, put in your dev login details and enable Dev Mode Status.

You will be asked to reboot so do it.

At next reboot enter again that app, enable also Key Server and note down IP address and passphrase both displayed on the left side.

Uninstall the official YouTube app from the TV (you won't be able to run the modified app without doing this).

Go to your computer and head to https://github.com/webosbrew/dev-manager-desktop/releases to download and install the latest release of Device Manager for webOS.

Follow the instructions at GitHub to setup a session to connect to your TV (basically give it a name, enter both the IP and the passphrase I told you to note down before and you are done) and connect to the TV.

If everything went well you should be connected so while having selected Apps in the left panel be sure to select also Available on top.

Look for Homebrew Channel in the list and click Install.

Go again to your TV, launch Homebrew Channel and there you will be able from now on to install or update YouTube AdFree and several other apps like ie. Hyperion for webOS.

Disclaimer:

The downside of this method is that every 1000 hours you do need to hit the EXTEND button in the Dev app