Hi @jonas_llubi, @Abt. I share you frustration with this. In fact, I spent the last 6 hours vibe coding an AI-assisted solution for a SIOC script that correctly handles the COM1/2 active/standby frequencies for both 25kHz and 8.33kHz frequencies.
I also changed the logic so that it truly does work as a slave device, in that if MSFS changes the frequency itself (or another app like BATC etc does) then the updated frequency will appear in the panel, and it won't keep overriding MSFS.
Limitations:
It's really nasty code, made with the assistance of AI. Works with MSFS2020, but not yet tested for MSFS 2024.
The SIOC script also doesn't appear to work for the Nav radios. I based it off the originally provided SIOC scripts from opencockpits (I'm not sure if I can share it openly with you, but there is no copyright notice on the original), and that original script doesn't work for Nav radios in MSFS2020 either. For me, the COM 1/2 radios were much more important. I can revisit the NAV modes later perhaps.
In testing, the display does sometimes go black, and the panel appears to fail. To fix it, you have to just press the "Reload" button in the SIOC utility. I changed the logic so that it always initialises with the active COM1/2 frequencies from MSFS so that it doesn't reset anything if you have to restart multiple times in the middle of a flight.
I hope it works as a stop-gap until something better comes along though!
Edit:
The NAV VOR and ADF radios don't work, but the ILS mode frequency and course values do work!
If you're interested, let me know and I can send the script to you privately.
Linguini