Compiling o/web.o....
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/libgd.a(gd_png.o): in function `gdPngReadData':
(.text+0x22): undefined reference to `png_get_io_ptr'
/usr/bin/ld: (.text+0x47): undefined reference to `png_error'
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/libgd.a(gd_png.o): in function `gdPngErrorHandler':
(.text+0x72): undefined reference to `png_get_error_ptr'
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/libgd.a(gd_png.o): in function `_gdImagePngCtxEx':
(.text+0x135): undefined reference to `png_create_write_struct'
/usr/bin/ld: (.text+0x14b): undefined reference to `png_create_info_struct'
/usr/bin/ld: (.text+0x188): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: (.text+0x1e1): undefined reference to `png_set_write_fn'
/usr/bin/ld: (.text+0x1ef): undefined reference to `png_set_compression_level'
/usr/bin/ld: (.text+0x253): undefined reference to `png_set_pHYs'
/usr/bin/ld: (.text+0x2ae): undefined reference to `png_set_IHDR'
/usr/bin/ld: (.text+0x4a7): undefined reference to `png_set_IHDR'
/usr/bin/ld: (.text+0x4e3): undefined reference to `png_write_info'
/usr/bin/ld: (.text+0x4ed): undefined reference to `png_set_packing'
/usr/bin/ld: (.text+0x54c): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: (.text+0x62b): undefined reference to `png_write_image'
/usr/bin/ld: (.text+0x63a): undefined reference to `png_write_end'
/usr/bin/ld: (.text+0x6af): undefined reference to `png_write_image'
/usr/bin/ld: (.text+0x6be): undefined reference to `png_write_end'
/usr/bin/ld: (.text+0x6dd): undefined reference to `png_set_tRNS'
/usr/bin/ld: (.text+0x76a): undefined reference to `png_set_PLTE'
/usr/bin/ld: (.text+0x816): undefined reference to `png_set_tRNS'
/usr/bin/ld: (.text+0x939): undefined reference to `png_write_image'
/usr/bin/ld: (.text+0x948): undefined reference to `png_write_end'
/usr/bin/ld: (.text+0xa9c): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/libgd.a(gd_png.o): in function `gdPngWriteData':
(.text+0xac1): undefined reference to `png_get_io_ptr'
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/libgd.a(gd_png.o): in function `gdImageCreateFromPngCtx':
(.text+0xb70): undefined reference to `png_sig_cmp'
/usr/bin/ld: (.text+0xb94): undefined reference to `png_create_read_struct'
/usr/bin/ld: (.text+0xbaa): undefined reference to `png_create_info_struct'
/usr/bin/ld: (.text+0xbe7): undefined reference to `png_destroy_read_struct'
/usr/bin/ld: (.text+0xc2b): undefined reference to `png_set_sig_bytes'
/usr/bin/ld: (.text+0xc41): undefined reference to `png_set_read_fn'
/usr/bin/ld: (.text+0xc50): undefined reference to `png_read_info'
/usr/bin/ld: (.text+0xc87): undefined reference to `png_get_IHDR'
/usr/bin/ld: (.text+0xd0e): undefined reference to `png_destroy_read_struct'
/usr/bin/ld: (.text+0xd80): undefined reference to `png_get_valid'
/usr/bin/ld: (.text+0xdc6): undefined reference to `png_set_packing'
/usr/bin/ld: (.text+0xdd6): undefined reference to `png_set_gray_to_rgb'
/usr/bin/ld: (.text+0xdea): undefined reference to `png_get_valid'
/usr/bin/ld: (.text+0xe0b): undefined reference to `png_read_update_info'
/usr/bin/ld: (.text+0xe1a): undefined reference to `png_get_rowbytes'
/usr/bin/ld: (.text+0xed9): undefined reference to `png_read_image'
/usr/bin/ld: (.text+0xee5): undefined reference to `png_read_end'
/usr/bin/ld: (.text+0xfca): undefined reference to `png_destroy_read_struct'
/usr/bin/ld: (.text+0x10e0): undefined reference to `png_get_valid'
/usr/bin/ld: (.text+0x1100): undefined reference to `png_get_tRNS'
/usr/bin/ld: (.text+0x1155): undefined reference to `png_get_PLTE'
/usr/bin/ld: (.text+0x1169): undefined reference to `png_get_valid'
/usr/bin/ld: (.text+0x1190): undefined reference to `png_get_tRNS'
/usr/bin/ld: (.text+0x121e): undefined reference to `png_set_strip_16'
/usr/bin/ld: (.text+0x124a): undefined reference to `png_get_pHYs'
/usr/bin/ld: (.text+0x12cd): undefined reference to `png_get_tRNS'
/usr/bin/ld: (.text+0x14cd): undefined reference to `png_destroy_read_struct'
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:139: afkmud] Error 1
make[2]: Leaving directory '/home/elwood/afkmud/src'
make[1]: *** [Makefile:128: all] Error 2
make[1]: Leaving directory '/home/elwood/afkmud/src'
make: *** [Makefile:171: clean] Error 2
elwood@godwars:~/afkmud/src$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 11.4.0-1ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-11 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-gcn/usr --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu --with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04)

I ain't admin so i can't do much with packages...

For anyone with this issue...

Add:

-lpng 

to L_FLAGS

Might be a bit late on this one but that's very odd that it would make you add an extra link flag. Unless it was specific to Ubuntu 22.04 - my system is on 24.04.1 now.

The libgd package should have been enough.