UHD Channels are using H265/HEVC, that is managed by the chipset of the box (motherboard).

The DM8000HD is managing MPEG, MPEG2, MPEG4/H264, but NOT HEVC/H265.

So in a DM8000HD you will be able to see channels up to H264.

Concerning the Tuner, it's highly possible that the chipset on it is not supported on older DM drivers (Mostly Broadcom). On latest versions of drivers some ST chipset were supported. See the /lib/modules/...../extra folder.

TS
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DM8000, DM800se, DM500HD, DM800HD, DM7025, DM7020s, DM7000, DM500s
VU+ Solo, VU+ Uno, VU+ Duo, Kathrein UFS910
Tivusat, TNTSat, Fransat, SSR/TSR, BBC1-2-3/ITV
DE-OpenBlackHole 1.4 image : http://www.openblackhole.com/