That LNB should work fine for listening to wideband stuff not requiring good frequency stability.
It will not work for TX without modifications. The LNB has a 4.5GHz DRO local oscillator. As evidenced by the ±1.5MHz frequency stability quoted by the manufacturer and the glued tuning screw on top of the DRO oscillator.
So for narrowband stuff or stuff requiring good stability (CW, SSB, DATV, satcom and so on) it would need to be modified with a more stable LO. One easy/cheap option would be one of those ADF4351 synthesizer boards from ebay and some arduino board from the same source.
One interesting option is using one of the LimeSDR TX outputs as a stable LO for the converter.
If one wants to transmit trough the LNB, the LNA and post mixer IF amplifier would need to be removed and jumpered with some coax. Then it would be bidirectional with some loss (easily 10dB loss). or one LNB modified for TX and the other kept as stock. But the price starts to rise fast. At that point it might become economical to just buy a transverter or receive converter from Kuhne/DB6NT.
Kuhne also has transmit converters.
As for the SUP-2400 converters and their mods. I have some of them waiting for time. I’m interested in seeing how well they perform after modifications. If nothing else the SUP-2400 will be more stable than the custom LNB.
But I’m worried how well the mixer will perform on C-band.
As the converter is originally made for converting 250-750MHz up to L-band.
One option for going above 3.8GHz is also PLL locked C-band satellite TV LNB’s. One should be able to get one for under 40eur. They are made for 3.4-4.4GHz, exact frequency coverage and how wide filters are varies between models.
I have one from Aliexpress for 3.4GHz reception with my scanners and rtl-sdr.
An additional option for the crafty person would be buying one of those 5.8GHz video receiver modules on ebay, removing the 480MHz IF filter and tapping the IF output. The bad thing is that the frequency reference on those is a normal 8MHz crystal and the LO in the chipset used has quite a bit of phasenoise, not a problem for video or FM audio, but performance is degraded for other uses.
While not a professional RF engineer, I do like my GHz.