Partly success on the HD Line Black Premium LNB. Inspired by OH2AUE's work.
Remove carefully the crystal and insert a simple bandpass as seen in the pictures.
Check if you have damaged the connection from the crystal pad to the via, if it is broken use a small wire to fix it.
Now the LNB could be used on both outputs with the external ref injected to the one you had choosen for connecting the bandpass.
The ext ref i use is the cheap toyocom TCXO from eBay which i have indoors and temperature isolated so it is relative stable (+/- 100Hz/h). The signal is fed with the known triplexer into the coaxial cable to the LNB.
With the 26MHz ref from the TCXO now the WB is shifted to the normal receiving range from a normal Sat receiver. (abt 1,106GHz)
It seems that the LNB gain has dropped abt 3dB, not a problem on my big dish, but on smaller dishes it would be not good. Maybe some additional resistors could improve the gain.