read last few pages... a lot discussed... in summary:

older batch of tx3mini is android7 with option to close root.
new batche is android8, no option to close root.
closing root is required to run unifi playtv or astrogo apps.
closing root with superSU or others can be tricky, can brick yr box, so do be careful.

there are sellers now offering a choice of android7 or 8, read back.

check with yr seller - either is not actually unrooted or unrooting failed or incomplete.
then again, if seller is not local, never used playtv or astrogo, he may not understand the problem.
i do not know enough of this tx3 mini android8 firmware, can't comment more.
like another user, u can try to sell off this one and buy another android7 - it's only rm105.
pls, pls, read back - al ot has been said, useful info.
this box firmware, like many others, is not compatible with the app, u won't find in playstore.
there are only a few that can do that, just like u can get direct with mobile phones and

tx3 mini - no.
tx3 max - yes.

It depends on the firmware I guess. My "old" TX3 mini got bluetooth with the 8.1 firmware. The new one I haven't test yet, but I suspect it doesn't have the support since all the firmware that the seller try to send have "no bluetooth" as a part of their naming. LOL