Download the Revanced Manager. Tap on the 'Patcher' tab at the bottom. Tap on 'Select an Application'. Look for YouTube. If it's not there at the top then search for it. That box that showed YouTube will also show what version of the YouTube app you have installed and what version they recommend you install so you can patch it. This is where it gets complicated.
Go to your web browser and search for 'YouTube apk'. I usually use apkmirror for my downloads but if anyone has another suggestion that's better, go for it. Tap on the link to go to the YouTube apk page on apkmirror and scroll down the page until you find the version number that matches the one listed in Revanced Manager. Tap on the downward-facing arrow icon and it will take you to the page for that version of YouTube. Scroll down and it will show you the different variants available for that version. Tap the download icon next to the variant that says 'no-dpi' and it will take you to that variant's download page. Scroll down and tap on the download button; this button will also display the size of the apk which should be around the 120-ish MB range. When the download is finished a little window should popup asking if you would like to open the file. DO NOT open the app yet. At this point you are going to switch back to Revanced Manager.
Hopefully you're still on the Select an application screen. If not then follow the instructions in the first paragraph until you are. At this point the installed and recommended version of YouTube should match. If it doesn't, that's okay. Tap on YouTube and a window might pop up asking to select the apk file. Find the file you downloaded if you need to. Then tap the 'Patch' button and let it run. It will take a few minutes and it will look like it's stalled out at times but it's not. Just let it go until it's done. Tap 'Install'. If it asks if you want to upgrade YouTube then tap 'Upgrade'.
Download the Revanced Manager. Tap on the 'Patcher' tab at the bottom. Tap on 'Select an Application'. Look for YouTube. If it's not there at the top then search for it. That box that showed YouTube will also show what version of the YouTube app you have installed and what version they recommend you install so you can patch it. This is where it gets complicated.
Go to your web browser and search for 'YouTube apk'. I usually use apkmirror for my downloads but if anyone has another suggestion that's better, go for it. Tap on the link to go to the YouTube apk page on apkmirror and scroll down the page until you find the version number that matches the one listed in Revanced Manager. Tap on the downward-facing arrow icon and it will take you to the page for that version of YouTube. Scroll down and it will show you the different variants available for that version. Tap the download icon next to the variant that says 'no-dpi' and it will take you to that variant's download page. Scroll down and tap on the download button; this button will also display the size of the apk which should be around the 120-ish MB range. When the download is finished a little window should popup asking if you would like to open the file. DO NOT open the app yet. At this point you are going to switch back to Revanced Manager.
Hopefully you're still on the Select an application screen. If not then follow the instructions in the first paragraph until you are. At this point the installed and recommended version of YouTube should match. If it doesn't, that's okay. Tap on YouTube and a window might pop up asking to select the apk file. Find the file you downloaded if you need to. Then tap the 'Patch' button and let it run. It will take a few minutes and it will look like it's stalled out at times but it's not. Just let it go until it's done. Tap 'Install'. If it asks if you want to upgrade YouTube then tap 'Upgrade'.
Once that's done you're good to go.