Have you tried changing DVB drivers to dvb-latest?
Yes I have. I tried CoreElec default drivers, DVB drivers for TBS and DVB drivers from the latest kernel, in all of them it shows as DVB-T in TVHeadend.
dvb-latest uses drivers from the latest kernel so if that doesn’t work then we are limited in what we can do.
We can try to patch default/latest drivers if a driver exists for your adapter.
How can I install dvb-latest?
Program Add-on / CoreELEC Module Drivers
I noticed that RTL2832 is used for both DVB-T and ISDB-T.
Just a side-note, RTL2832 is used also in Astrometa DVB stick, and I believe it works fine (for DVB-T) with v4l media build drivers. I am using panasonic mn8873 although within the same stick, because it supports also DVB-T2.