Someone is offering to mod TX6 out there to work with this Lemlive/Movie app for a fee few months back.
This person is an insider working for Long TV with access to their MAC ID whitelist database.

Earlier it worked with TX6 boxes because both the Long TV box and TX6 boxes because they had the same Allwinner H6 chipsets inside them but the Long TV box were restricted only with a small 1GB size RAM. The TX6 boxes with 2GB/4GB variants worked much better then stock Long TV boxes.
They shared similar MAC IDs but can still be differentiated because of batches.

Until recently they figured a way to block TX6 boxes by identifying the batch of MAC ID blocks only assigned to Long TV boxes and if needed whitelist other boxes manually into their system.

When you have an insider in your company doing side business inputting MAC IDs manually into their database, you know it's not going to last long. Maybe this company is about to go bankrupt or out of business.

The other larger networks such as EVPad are branching out into subscription based services IPTV named Happy TV to reach a larger audience by allowing EVPad type service to be installed on OEM android tv boxes.

Thanks for the correction my bad but why the TX6 was the targeted OEM device for the LemLive/Movie app?

Through observation, it was noticed that many of their reseller shops that were selling Long TV "Louie" boxes were also selling Eplay 3R boxes which were clone variants of EVPad 3S boxes (both claimed to be MCMC approved).

Could the Lemon apps were initially targeted to be pushed to both these 2 boxes brands but only to later find out that granting access to Eplay 3R opened up backdoors for other Allwinner H6 boxes out there to gain access to them with similar MAC IDs ?

T6X was among the most popular OEM Allwinner H6 boxes at the time taking advantage of this loophole. The other H6 chipset boxes namely the EVpads, iBoite and even SVI Cloud boxes never bothered because they have superior exclusive applications to go with them.

Resetting or removing any app won't help here since the source of advertisement is coming from a system app which is integral part of your tv box.

No antivirus or ad blocker is going to block these ads because the system app bypasses them with a proxy which connects back to a China ad server.

My BIGGEST suspect is the Alice UX launcher itself which is the source of this ads which is allowing the backdoor to happen. Unless you know how to replace your tv box's launcher, nothing can be done.