[Android Apps and Games] zgfg:
I can give you general steps but you will need to download and find parts by yourself and you must be familiar in using a root explorer (I use the excellent MiXPlorer) - for that, please research on your side if you need more info:

1) Use Vanced Manager and uninstall your Vanced app (root 17.03.38) - not just the Vanced mngr (you will later uninstall mngr when you're done)

I think the Manager does not fully clean, hence you need to manually do the step (2)

2) Use root explorer (like MiXPlorer) and go to:

/data/adb

I don't have the Vanced app installed by Mngr hence cannot give you the full/correct names of the files, but you will find them:

- There is a Vanced subfolder (I think it was the name) and inside the base.apk file - rename that base.apk to base.bak

- There are also two subfolders in /data/adb, one service.d and the other post-fs-data.d

In both subfolders there will be some vanced.sh or so sh scripts (there might be sh files from AML or something else, do not touch those other sh files)

Rename those vanced.sh files (might be the names are little different but they must belong to Vanced) to vanced.bak

(Later when you reboot and find that everything is ok, you can delete those three renamed *.bak files)

It could be that the new Vanced Mngr now correctly removes those files when you take Uninstall Vanced app, but previously it didn't - hence you must manually check and delete if Mngr would not remove them properly

3) Reboot!!!

Go to the native Settings, Manage apps, search for YouTube and take Uninstall (or at least Uninstall updates if it doesn't allow to Uninstall)

It depends did you have YT preinstalled in the ROM, etc - but as a result:

- you must have no more YouTube installed

-or, at least, your installed YouTube must be older than 16.29.39

Without that, you will not be able to roll-back to Vanced root 16.29.39

Make sure that you have disabled Auto updates for YouTube in Google Play or even better, that YouTube is detached from Google Play (out of scope for my guide here and my time, search in this thread how to do detaching)

----

Now reboot again, double-check that there is no YouTube or no YouTube 16.29.39 or newer installed to your phone

Then:

3) Go to apkmirror and find YouTube 16.29.39 SPLIT app and download - it will be an APKM file

To install that apkm, you will need Apkmirror installer - find/download the installer on their site and install, then install the downloaded YT 16.29.39 apkm

If you're not familiar with, google about split (aka bundle) app installations

4) After that you will have the official YT 16.29.39

Do not open/run YT yet!!!

Make sure that Google Play would not update YT to the latest (see about detaching as above)

5) There was recently (last days, since it was announced that Vanced shuts down) a post pointing to an older post with the Vanced root versions repackaged to the Magisk modules

From that older post (or find it yourself in the thread), download the Vanced 16.29.39 in Magisk module

After installing that Magisk module, then reboot!!!

That post may also contain the link to the official YT 16.29.39 from apkmirror - saving you time for the step (3), and also the guide for steps (3) and (5) as above (with more details there)

With that Magisk module and after rebooting (every module installation/update/uninstalling requires reboot), open the YouTube - you should find then that you hace the Vanced root 16.29.39 app

But again, use detaching to make sure that Google Play never updates the YT - if it does, you will loose Vanced root and you should then repeat steps 3, 4 and 5 (every time when Google Play updates YT)

Good luck

PS: Vanced root repackaged to Magisk modules are in the post #19305:

https://xdaforums.com/t/app-mod-root-nonroot-vanced.3758757/page-966#post-85452853