Error: no longer provides linux-compiler-gcc-6-x86

I have kernel 4.9 on Debian 9. Yes, I know it's old.

Now I'm trying to install 4.19. It is available here:

http://archive.debian.org/debian/pool/main/l/linux/

There has been a little bit of dependency hell, but I could find and install seven packages so far.

Now I've hit a harder obstacle. The package is linux-headers-4.19.0-0.bpo.9-amd64_4.19.118-2+deb10u1~bpo9+1_amd64. I always test each package with GDebi because it tells me the dependencies before installing. It complains:

Error: Dependency is not satisfiable: linux-compiler-gcc-6-x86 (>= 4.14.17~1)

OK, I ran into similar error seven times before and always found the missing package. But this time I could only find linux-compiler-gcc-6-x86_4.19.118-2+deb10u1~bpo9+1_amd64.deb and I thought it would work because 4.19 >= 4.14, right?

But GDebi complains:

Error: no longer provides linux-compiler-gcc-6-x86
Compiler for Linux on x86 (meta-package)
This package depends on GCC of the appropriate version and architecture for Linux on amd64, i386 and x32.

I can't even find "no longer provides" on google. I've read some unhelpful pages, even more unhelpful because all I have is the linux-compiler-gcc-6-x86_4.19.118-2+deb10u1~bpo9+1_amd64.deb package.

Is there some way to proceed?