The last version (4.2.7) DVB Viewer Pro, published in early August, has solved a major problem of dual tuner/dual CI TBS66880.
For viewing the scrambled channels this tuner requires the dynamic library tbsCIapi and for simultaneous function of both tuners requires two such libraries.
The last version of the DVB Viewer allows you to clone this library, for the correct function of the card TBS6680 you need to use tbsCIapi and its clone tbsCIapi1. (copy tbsCIapi.dll > paste and rename it to tbsCIapi1.dll).
DVB-C dual tuner/dual CI TBS6680 is working satisfactorily with these two dynamic link libraries. Unfortunately, DVBViewer Recording Service 1.26, whose development was suddenly interrupted, does not support the simultaneous function of both tuners.
I gather that a similar problem also appears on the DVB-S/S2 dual tuner/dual CI and using a DVB Viewer can solve this problem. Dynamic-link library support for the TBS cards use other programs like ProgDVB, DVBDream and TBS Viewer (a clone of the DVB Viewer) but I don't know whether and how the issue is resolved.
In General, it is possible to create a library of tbsCIapi to tbsCIapin, where n is the number of tuners -1.