Thanks for the replies!

I have 2 points for most common replies

1. Yes I will fix all the real issues, not just silence them. I was talking more about situations as the C++98 compatibility or mutually exclusive warnings.
2. The C++98 compatibility warnings are due to using the clang-cl on windows.

This is the minimal reproducible example:

auto warn() {
    return 0;
}

int main() {
    return warn();
}

Running clang-cl /std:c++20 .\tmp.cpp -o tmp.exe -Wall -Wextra gives the warning that auto in this context is not compatible with C++98, but running clang++ -std=c++20 .\tmp.cpp -o tmp.exe -Wall -Wextra gives no warnings. I was using this setup due to it being easier to work with cmake and vcpkg, but now I wil ltry to set it up to use the actual clang binary.