I am not absolutely certain that what i am going to say applies to your case but this ground has been gone over many times before.
These cheap internal tuners have a chip which can feed the demuxed signal to the tuner in one of two ways, single lane serial or multi-lane parallel. The standard Linux driver is configured to use the parallel interface but some of the manufacturers (khadas to name one) chose to go single lane serial. The Linux driver simply doesn’t work with the serial interface and does exactly what you describe - never tunes the muxes.
We once had a developer who worked on this problem and got the standard linux driver to work with the serial interface - but he went silent two years ago.
This whole area is a minefield and there are very few people with the expertise to reverse engineer the closed source manufacturer drivers. The manufacturers and chip developers produce one driver and then abandon all further development, they never release open source drivers. CE have made an executive decision that they will not support these obscure cheap chipsets as it is a total resource sucker. LinuxTV (the linux project which supports dvb hardware) is a dying project as all the tech-geeks who devoted their time to getting sat hardware working now realize that IPTV does everything better if you have a half decent broadband connection.
It is now standard practice for the CE team to only recommend the standards based SAT > IP hardware.
Shoog