yep, setting PKG_CONFIG_PATH would fix it as expected

[root@majortheobaldslapper:/build/source]#  PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 pkg-config --libs --cflags fuse3 fuse3>=3.0.0

[root@majortheobaldslapper:/build/source]# echo $?
0

[root@majortheobaldslapper:/build/source]# unset PKG_CONFIG_PATH

[root@majortheobaldslapper:/build/source]#  PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 pkg-config --libs --cflags fuse3 fuse3>=3.0.0
Package fuse3 was not found in the pkg-config search path.
Perhaps you should add the directory containing `fuse3.pc'
to the PKG_CONFIG_PATH environment variable
No package 'fuse3' found
Package fuse3 was not found in the pkg-config search path.
Perhaps you should add the directory containing `fuse3.pc'
to the PKG_CONFIG_PATH environment variable
No package 'fuse3' found

In reply to @staberinde:matrix.org

Currently I have

borg-tui = pkgs.rustPlatform.buildRustPackage (finalAttrs: rec {
    pname = "borgtui";
    version = "fdcf13ba063a9e8516e5bc5f679af5504304819d";
    src = pkgs.fetchFromGitHub {
      owner = "dpbriggs";
      repo = pname;
      rev = version;
      sha256 = "7UbwW53HTM4oTbDnNruwjtF0KrnhoiCYXWl0CbXfMSk=";
    };
    nativeBuildInputs = [
      pkgs.pkg-config
    ];
    bulldInputs = [
      pkgs.fuse3
    ];
    cargoHash = "sha256-7F87unpr3OoY9SFBS2iwKhk2khYKH5w5xaENHUwnqC0=";
  });

In reply to @k900:0upti.me
What do you mean by "check the output"?

In reply to @k900:0upti.me
For every architecture