> while in the C language structures with virtual function tables that are accessed explicitly by the programmer are in widespread use wherever suitable, for instance in many popular open-source C programs, like the Linux kernel or the debugger gdb

For dynamic dispatch there is absolutely no difference between using a jump table in C and virtual method tables in C++. If the compiler can infer the target address at compile time, it will not go through an indirect call, e.g.:

https://www.godbolt.org/z/as8ehGhv3

And for 'static dispatch' there's no difference between a C++ method call and a direct C function call (since for static dispatch the caller needs to 'know' the target function either way).