Debugger depends on environment.
FPC (the compiler) does not have any bindings to any gdb or other debugger.
FP (the FPC IDE) use gdb. It used to be libgdb, but now on most targets supposedly is just a gdb instance.
If a gdb instance, then it may be possible (but I do not know) to substitute the gdb exe with a different version.
That said, newer isn't always better, but a matter of trial and error.
All the rest about debugger, is not FPC related. FPC (the compiler) just provides debug info. => OFF TOPIC
The Lazarus IDE comes with FpDebug (for Linux and Windows, and only INTEL/AMD CPU).
For the rest it is gdb. On Linux it uses what is installed by the repo. On Window it still ships an old one, but if you have a newer, well test it.
On Mac, it uses a combination of LLDB+FpDebug (even with the M CPUs).