How to use a custom debugger (not VS, VS code, or Rider) in Unity?

Is there any way to run a custom debugger (not VS, VS code, or Rider) in Unity? My debugger only needs an executable and a pdb file. Unity compiles C# code into DLL and calls it so I wonder if they ever document any API to attach a program to the debugging process.

You can attach something like lldb to the Unity editor executable and it should work if it can find symbol information. Unfortunately I’ve found that attempting to detach lldb or stop it will crash Unity.

Can you elaborate more on it? How does the attach process work?