Yeah, that is why I mentioned closing the root is only part of the solution.
I think the proper hardware or correct rom/kernel is also required for it to work along with mod apks.
I don't think all Tx3 mini are build the same.

I read there are Tanix branded tx3, original OEM hardware tx3, there are also unofficial hardware copies of tx3 manufacturers, and some even sells refurbished boxes (dunno what it is meaning of refurbished??).

But I got Astro and Unify working using the tx3 mini I bought from the seller mentioned in my earlier post.

Let me get this straight first, I am just an end-user like many in here. I could feel your frustrations of trying to get your Tx3 Mini to run AstroGo. I consider myself extremely lucky to have bought my Tx3 mini from THIS SELLER [click here], and not have to go through the experience you went through. Albeit I was prepared to experiment in case it didn't work, if too bad - I just take the RM118 as a total loss and get another box. Alas, my Tx3 only needed a setting change and a modded apk to work. I sincerely do not if the seller has made any modifications prior delivery and didn't tell me about it.

For your case, I would advise you to go straight back to your seller and ask for guidance. However I sincerely doubt they even know or have the expertise. Even if they know, a lot of them I notice would not divulge these trade secrets. I can understand that this is their rice and bowl and very hesitant to tell. In the past 4 months, I have met with people like you asking for help in facebook groups. There are online sellers that bluntly tell them, to google about it and the sellers are hesitant to spell it out step by step.

At the very best, they will give some very vague hints, or general process. When asks for more info, they won't respond anymore.

I can tell you everything here of what I do know.

There are essentially 2 other ways apart from the one I have performed that uses mod APK.
1) I am sure you have read apps.atvxperience.com. In there there is some guide on how to install TWRP and reroot with MagisK to hide root from any apps you want.

2)Unroot the box and thus can use official app.
Method a) Edit build prop. Then delete system file
Method b) Edit build prop. Use SuperSU(V2.xx)

there are other mothods as you mentioned, app exposed n rootcloak. Sometimes reported works, others don't.
Others even reported using the SuperSU and tap full unroot works, but again it only works when the proper hardware, kernel and SuperSU version is correctly employed. Other wise soft brick will happen whereby the box cannot boot up.

Google about it, or consult your supplier.
Other wise just get another cheap box that runs AstroGo and Unifi and nothing else.
[Click Here RM88 ONLY] for a 1GB RAM 8 GB ROM just to run Astro and Unifi.