Reverse engineering Control panel to control with a pi

On the picture of the bare PCB on the right you see a voltage regulator. then in the middle a CPU and on the left a shift register. The small 8pin chip is an EEPROM.  So the CPU will have control over the 20 leds.

When you report measuring near 400MHz with a DSO nano, something is going wrong between your electronics and it being reported here on this forum. So I also doubt the "10V signals" that you mention: I expect microcontroller-compatible signal levels because the signal wire goes directly from the connector into the microcontroller.

You can achieve your goal through two possible routes. Which one is going to be most easy I don't know in advance.

The first route is to analyse the signal. and reproduce that on the pi.

The other route is to simply wire the pi to emulate button presses on buttons.  Double check: All switches have a connection to GND, and double check that they have a connection to the little CPU.

Maybe a little more can be learned from the name of the CPU. The EEPROM I can read the text on it in your picture, but not of the other chips. Can you take another picture where we can read the numbers on the other chips?

Note that reverse engineering is not a skill that you can explain to someone step-by-step. It requires someone with a bit of intelligence doing the actual job. There have been a few stories on hackaday that were listed because the person did some clever reverse engineering. Read up on those articles is what I'd suggest.

I'll check the voltage I'm guessing I'm wrong as I didn't test voltage just set 10v on ossiloscope to make it clearer , I Wana get rid of that controller make my owner in form of GUI on touch screen controller I'm guessing my discription sucks that controller controls a beacon bar on the roof of my van 6 strips at the back and 6 at front and 1 eather side of the bar the only way to control the beacon bar is with this control panel ( no on off switch ) and my ultimate goal using relays and this controller is to have a GUI interface to control the van top to bottom clean no buttons or switch's and then move it to a large center touch screen in middle of van for stereo custom 3d printed parts so will be like Tesla but I got year before I get brand new van and will use current beacon bar I have due to being brighter than what out police force have , I can require a van or car to do what I want as it's simple relay job for each part

I'll check the voltage I'm guessing I'm wrong as I didn't test voltage just set 10v on ossiloscope to make it clearer , I Wana get rid of that controller make my owner in form of GUI on touch screen controller I'm guessing my discription sucks that controller controls a beacon bar on the roof of my van 6 strips at the back and 6 at front and 1 eather side of the bar the only way to control the beacon bar is with this control panel ( no on off switch ) and my ultimate goal using relays and this controller is to have a GUI interface to control the van top to bottom clean no buttons or switch's and then move it to a large center touch screen in middle of van for stereo custom 3d printed parts so will be like Tesla but I got year before I get brand new van and will use current beacon bar I have due to being brighter than what out police force have , I can require a van or car to do what I want as it's simple relay job for each part