Fix XFCE4 themeing on newer than 4.12

tl;dr
You can not set appearance on anything running on XScreens other than 0.0.

inxi -Faz Output:

System:
  Kernel: 5.10.79-1-lts x86_64 bits: 64 compiler: gcc v: 11.1.0
  parameters: BOOT_IMAGE=/@/boot/vmlinuz-linux-lts
  root=UUID=b0e4d9bb-6152-4407-bf73-0dbf7d629019 rw [email protected] quiet
  splash rd.udev.log_priority=3 vt.global_cursor_default=0
  systemd.unified_cgroup_hierarchy=1 loglevel=3
  Desktop: Xfce 4.16.0 tk: Gtk 3.24.29 info: xfce4-panel wm: xfwm 4.16.1
  vt: 7 dm: LightDM 1.30.0 Distro: Garuda Linux base: Arch Linux
Machine:
  Type: Desktop Mobo: Micro-Star model: B450 TOMAHAWK (MS-7C02) v: 1.0
  serial: <filter> UEFI: American Megatrends LLC. v: 1.H5 date: 04/22/2021
CPU:
  Info: 8-Core model: AMD Ryzen 7 2700X bits: 64 type: MT MCP arch: Zen+
  family: 17 (23) model-id: 8 stepping: 2 microcode: 800820D cache:
  L2: 4 MiB
  flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 svm
  bogomips: 118401
  Speed: 3441 MHz min/max: 2200/3700 MHz boost: enabled Core speeds (MHz):
  1: 3441 2: 4221 3: 3956 4: 4130 5: 3207 6: 4218 7: 4264 8: 4250 9: 3660
  10: 3542 11: 3430 12: 4226 13: 4072 14: 4154 15: 3557 16: 4070
  Vulnerabilities: Type: itlb_multihit status: Not affected
  Type: l1tf status: Not affected
  Type: mds status: Not affected
  Type: meltdown status: Not affected
  Type: spec_store_bypass
  mitigation: Speculative Store Bypass disabled via prctl and seccomp
  Type: spectre_v1
  mitigation: usercopy/swapgs barriers and __user pointer sanitization
  Type: spectre_v2 mitigation: Full AMD retpoline, IBPB: conditional, STIBP:
  disabled, RSB filling
  Type: srbds status: Not affected
  Type: tsx_async_abort status: Not affected
Graphics:
  Device-1: NVIDIA GP106 [GeForce GTX 1060 6GB] vendor: ZOTAC driver: nvidia
  v: 495.44 alternate: nouveau,nvidia_drm bus-ID: 25:00.0 chip-ID: 10de:1c03
  class-ID: 0300
  Device-2: NVIDIA TU116 [GeForce GTX 1660] vendor: ZOTAC driver: nvidia
  v: 495.44 alternate: nouveau,nvidia_drm bus-ID: 26:00.0 chip-ID: 10de:2184
  class-ID: 0300
  Display: x11 server: X.Org 1.21.1.1 compositor: xfwm4 v: 4.16.1 driver:
  loaded: nvidia display-ID: :0.0 screens: 3 default screen: 0
  Screen-1: 0 s-res: 5760x1080 s-dpi: 96 s-size: 1524x286mm (60.0x11.3")
  s-diag: 1551mm (61")
  Monitor-1: DP-0 res: 1920x1080 hz: 60 dpi: 93 size: 527x296mm (20.7x11.7")
  diag: 604mm (23.8")
  Monitor-2: DP-2 res: 1920x1080 hz: 60 dpi: 93 size: 527x296mm (20.7x11.7")
  diag: 604mm (23.8")
  Monitor-3: DP-4 res: 1920x1080 hz: 60 dpi: 93 size: 527x296mm (20.7x11.7")
  diag: 604mm (23.8")
  Screen-2: 1 s-res: 5760x1080 s-dpi: 95 s-size: 1540x292mm (60.6x11.5")
  s-diag: 1567mm (61.7")
  Screen-3: 2 s-res: 1280x1024 s-dpi: 85 s-size: 382x302mm (15.0x11.9")
  s-diag: 487mm (19.2")
  OpenGL: renderer: NVIDIA GeForce GTX 1660/PCIe/SSE2 v: 4.6.0 NVIDIA 495.44
  direct render: Yes
Audio:
  Device-1: NVIDIA GP106 High Definition Audio vendor: ZOTAC
  driver: snd_hda_intel v: kernel bus-ID: 25:00.1 chip-ID: 10de:10f1
  class-ID: 0403
  Device-2: NVIDIA TU116 High Definition Audio vendor: ZOTAC
  driver: snd_hda_intel v: kernel bus-ID: 26:00.1 chip-ID: 10de:1aeb
  class-ID: 0403
  Device-3: Focusrite-Novation Scarlett 6i6 type: USB driver: snd-usb-audio
  bus-ID: 1-8:3 chip-ID: 1235:8012 class-ID: fe01 serial: <filter>
  Sound Server-1: ALSA v: k5.10.79-1-lts running: yes
  Sound Server-2: JACK v: 1.9.19 running: no
  Sound Server-3: PulseAudio v: 15.0 running: yes
  Sound Server-4: PipeWire v: 0.3.40 running: yes
Network:
  Device-1: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet
  vendor: Micro-Star MSI driver: r8169 v: kernel port: e000 bus-ID: 22:00.0
  chip-ID: 10ec:8168 class-ID: 0200
  IF: enp34s0 state: up speed: 1000 Mbps duplex: full mac: <filter>
RAID:
  Supported mdraid levels: raid0
  Device-1: md127 maj-min: 9:127 type: mdraid level: raid-0 status: active
  size: 1.82 TiB
  Info: report: N/A blocks: 1953258496 chunk-size: 512k super-blocks: 1.2
  Components: Online:
  0: sda1 maj-min: 8:1 size: 931.51 GiB
  1: sdb1 maj-min: 8:17 size: 931.51 GiB
Drives:
  Local Storage: total: 3.87 TiB used: 1.97 TiB (51.0%)
  SMART Message: Required tool smartctl not installed. Check --recommends
  ID-1: /dev/nvme0n1 maj-min: 259:0 vendor: Western Digital
  model: WDS250G1B0C-00S6U0 size: 232.89 GiB block-size: physical: 512 B
  logical: 512 B speed: 15.8 Gb/s lanes: 2 type: SSD serial: <filter>
  rev: 201000WD temp: 38.9 C scheme: GPT
  ID-2: /dev/sda maj-min: 8:0 vendor: Western Digital
  model: WD1003FZEX-00K3CA0 size: 931.51 GiB block-size: physical: 4096 B
  logical: 512 B speed: 6.0 Gb/s type: HDD rpm: 7200 serial: <filter>
  rev: 1A01 scheme: MBR
  ID-3: /dev/sdb maj-min: 8:16 vendor: Western Digital
  model: WD1003FZEX-00K3CA0 size: 931.51 GiB block-size: physical: 4096 B
  logical: 512 B speed: 6.0 Gb/s type: HDD rpm: 7200 serial: <filter>
  rev: 1A01 scheme: MBR
  ID-4: /dev/sdc maj-min: 8:32 vendor: Western Digital
  model: WD10EFRX-68PJCN0 size: 931.51 GiB block-size: physical: 4096 B
  logical: 512 B speed: 6.0 Gb/s type: HDD rpm: 5400 serial: <filter>
  rev: 1A01 scheme: MBR
  ID-5: /dev/sdd maj-min: 8:48 vendor: Western Digital
  model: WD10EFRX-68PJCN0 size: 931.51 GiB block-size: physical: 4096 B
  logical: 512 B speed: 6.0 Gb/s type: HDD rpm: 5400 serial: <filter>
  rev: 1A01 scheme: MBR
Partition:
  ID-1: / raw-size: 232.38 GiB size: 232.38 GiB (100.00%)
  used: 9.66 GiB (4.2%) fs: btrfs dev: /dev/nvme0n1p2 maj-min: 259:2
  ID-2: /boot/efi raw-size: 512 MiB size: 511 MiB (99.80%)
  used: 576 KiB (0.1%) fs: vfat dev: /dev/nvme0n1p1 maj-min: 259:1
  ID-3: /home raw-size: 1.82 TiB size: 1.79 TiB (98.38%)
  used: 601.66 GiB (32.8%) fs: ext4 dev: /dev/md127p1 maj-min: 259:3
Swap:
  Kernel: swappiness: 133 (default 60) cache-pressure: 100 (default)
  ID-1: swap-1 type: zram size: 62.79 GiB used: 0 KiB (0.0%) priority: 100
  dev: /dev/zram0
Sensors:
  System Temperatures: cpu: 44.9 C mobo: N/A
  Fan Speeds (RPM): N/A
  GPU: device: nvidia screen: :0.0 temp: 38 C fan: 38% device: nvidia
  screen: :0.1 temp: 38 C fan: 38% device: nvidia screen: :0.2 temp: 38 C
  fan: 38%
Info:
  Processes: 426 Uptime: 21m wakeups: 0 Memory: 62.8 GiB
  used: 4.77 GiB (7.6%) Init: systemd v: 249 tool: systemctl Compilers:
  gcc: 11.1.0 Packages: pacman: 1288 lib: 347 Shell: Bash v: 5.1.8
  running-in: sakura inxi: 3.3.08

This isn't a Garuda specific issue but Garuda XFCE4 is the most functional I've come across since moving from Ubuntu 18.04. I am simply hoping someone can shed some light on what's going on and where the issue actually lies.

Themeing is broken on any xfce newer than 4.12. I've seen the code change where they stopped enumerating XScreens. I was hoping someone here might be able to help point me in the direction of actually fixing this and perhaps even submitting a patch, something I've never done before.