See my post immediately above. My cell plan does not support tethering using native apps because they detect it. I can't believe other people are not having issues like this...
I know you're not getting responses exactly to your query and situation; so here's my attempt -- although I'm unsure if they would be consider the "best root tether app"...
I figure, since you're asking for "root", you're probably looking for modules...
A quick google search popped up these top 3 results:
Tether Unlock Github (while last version released was '20, there are some people that still use Titanium Backup; you never know what still might work)
Tethering Enabler; This one is much older...I wonder how effective it might be. But you never know...
X Tether (Xposed Module); Another old one. I wonder if it might work -- especially considering Android OS version it was made for and/or if something like LSPosed might be able to take it on...
Point is, there are some options that you can try if you google with the search term "magisk" "module" & "tether" -- and although much of the results are out of date, it still might lead you to an unexpected solution or a newer development being done. Also, you could/should probably check out Magisk or LSPosed repositories. I know you were looking for the latest best -- especially considering you are posting in Google's latest device (if you don't consider the Fold yet) -- but apparently it's not something super actively developed on...
