DVB-T2 works (kind of) with TDA28218/CDX2820!
The driver for the TDA28278 finally works on my box. However, it seems that I could not tune in to DVB-T2 channels before due to a timing issue. For example, in the source file cdx2820.c there are lines such as
and similarly for the tda18272.c. I increased these pauses to 300 milliseconds and, after recompiling the related modules, I could receive DVB-T2 channels that I selected manually in E2. It is not stable yet, though; a full channel search sometimes misses some DVB-T2 channels. I will play around with these pauses/timeouts a bit. I also think that the issue with my DVB-S2 tuner that fails to select vertically polarized channels is a timing issue. This could explain that it works on Audioniek's hardware - mine is compatible but production tolerances for the hardware could make a difference. Will look into that later.Code:msleep(30); /* fixme: think on this */
Finally, I found this URL: https://patchwork.kernel.org/patch/3757251/ It indicates that TDA28278 is a superset of TDA28218; as far as I understand it just includes some additional modulations that E2 may not use anyway.