Report everything you have already attempted to solve your problem.
I have attempted substituting backgound_opacity: in ~/.config/alacritty/alacritty.yml and ~/.config/alacritty_themed/alacritty.yml with window.opacity: as the config warning suggests, but opacity was broken. I am not sure how window.opacity is implemented in the current (alacritty-git 1:0.10.0.1882.g58985a4d-1) version.
inxi -Faz
System: Kernel: 5.14.5-200-tkg-bmq x86_64 bits: 64 compiler: gcc v: 11.1.0
parameters: intel_pstate=passive BOOT_IMAGE=/@/boot/vmlinuz-linux-tkg-bmq
root=UUID=89b130b9-3b0e-4951-a8a9-05c1c131615a rw rootflags=subvol=@
cryptdevice=UUID=ced52dfa-6abb-4eed-8ed4-9015641e0caf:luks-ced52dfa-6abb-4eed-8ed4-9015641e0caf
root=/dev/mapper/luks-ced52dfa-6abb-4eed-8ed4-9015641e0caf splash rd.udev.log_priority=3 vt.global_cursor_default=0
systemd.unified_cgroup_hierarchy=1 resume=/dev/mapper/luks-c1a24b17-8dee-48a9-8c22-95a63bbe0589 loglevel=3
Desktop: KDE Plasma 5.22.5 tk: Qt 5.15.2 info: latte-dock wm: kwin_x11 vt: 1 dm: SDDM Distro: Garuda Linux
base: Arch Linux
Machine: Type: Desktop Mobo: ASUSTeK model: MAXIMUS IX HERO v: Rev 1.xx serial: <filter> UEFI: American Megatrends v: 1301
date: 03/14/2018
CPU: Info: Quad Core model: Intel Core i7-7700K bits: 64 type: MT MCP arch: Kaby Lake family: 6 model-id: 9E (158)
stepping: 9 microcode: EA cache: L2: 8 MiB
flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 67266
Speed: 4339 MHz min/max: 800/5000 MHz Core speeds (MHz): 1: 4339 2: 3742 3: 4375 4: 3338 5: 5000 6: 3044 7: 5000
8: 5001
Vulnerabilities: Type: itlb_multihit status: KVM: VMX disabled
Type: l1tf mitigation: PTE Inversion; VMX: conditional cache flushes, SMT vulnerable
Type: mds mitigation: Clear CPU buffers; SMT vulnerable
Type: meltdown mitigation: PTI
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 generic retpoline, IBPB: conditional, IBRS_FW, STIBP: conditional, RSB filling
Type: srbds mitigation: Microcode
Type: tsx_async_abort mitigation: TSX disabled
Graphics: Device-1: NVIDIA GP102 [GeForce GTX 1080 Ti] vendor: eVga.com. driver: nvidia v: 470.74
alternate: nouveau,nvidia_drm bus-ID: 01:00.0 chip-ID: 10de:1b06 class-ID: 0300
Display: x11 server: X.Org 1.20.13 compositor: kwin_x11 driver: loaded: nvidia display-ID: :0 screens: 1
Screen-1: 0 s-res: 4480x1440 s-dpi: 94 s-size: 1211x389mm (47.7x15.3") s-diag: 1272mm (50.1")
Monitor-1: HDMI-0 res: 1920x1080 hz: 60 dpi: 94 size: 521x293mm (20.5x11.5") diag: 598mm (23.5")
Monitor-2: DP-0 res: 2560x1440 dpi: 109 size: 598x336mm (23.5x13.2") diag: 686mm (27")
OpenGL: renderer: NVIDIA GeForce GTX 1080 Ti/PCIe/SSE2 v: 4.6.0 NVIDIA 470.74 direct render: Yes
Audio: Device-1: Intel 200 Series PCH HD Audio vendor: ASUSTeK driver: snd_hda_intel v: kernel bus-ID: 00:1f.3
chip-ID: 8086:a2f0 class-ID: 0403
Device-2: NVIDIA GP102 HDMI Audio vendor: eVga.com. driver: snd_hda_intel v: kernel bus-ID: 01:00.1
chip-ID: 10de:10ef class-ID: 0403
Device-3: Sennheiser GSX 1000 Main Audio type: USB driver: hid-generic,snd-usb-audio,usbhid bus-ID: 1-6:4
chip-ID: 1395:005e class-ID: 0300 serial: <filter>
Sound Server-1: ALSA v: k5.14.5-200-tkg-bmq 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: 0.3.35 running: yes
Network: Device-1: Intel Ethernet I219-V vendor: ASUSTeK driver: e1000e v: kernel port: f000 bus-ID: 00:1f.6
chip-ID: 8086:15b8 class-ID: 0200
IF: enp0s31f6 state: up speed: 1000 Mbps duplex: full mac: <filter>
Device-2: Intel Wireless 8260 driver: iwlwifi v: kernel port: e000 bus-ID: 04:00.0 chip-ID: 8086:24f3
class-ID: 0280
IF: wlp4s0 state: down mac: <filter>
Bluetooth: Device-1: Intel Bluetooth wireless interface type: USB driver: btusb v: 0.8 bus-ID: 1-14.1:8 chip-ID: 8087:0a2b
class-ID: e001
Report: bt-adapter ID: hci0 rfk-id: 0 state: down bt-service: enabled,running rfk-block: hardware: no software: yes
address: <filter>
Drives: Local Storage: total: 8.19 TiB used: 202.84 GiB (2.4%)
SMART Message: Unable to run smartctl. Root privileges required.
ID-1: /dev/nvme0n1 maj-min: 259:6 vendor: Samsung model: SSD 960 EVO 1TB size: 931.51 GiB block-size:
physical: 512 B logical: 512 B speed: 31.6 Gb/s lanes: 4 type: SSD serial: <filter> rev: 3B7QCXE7 temp: 37.9 C
scheme: GPT
ID-2: /dev/nvme1n1 maj-min: 259:0 vendor: Samsung model: SSD 960 EVO 250GB size: 232.89 GiB block-size:
physical: 512 B logical: 512 B speed: 31.6 Gb/s lanes: 4 type: SSD serial: <filter> rev: 3B7QCXE7 temp: 38.9 C
scheme: GPT
ID-3: /dev/sda maj-min: 8:0 vendor: Samsung model: SSD 850 EVO 1TB size: 931.51 GiB block-size: physical: 512 B
logical: 512 B speed: 6.0 Gb/s type: SSD serial: <filter> rev: 3B6Q scheme: GPT
ID-4: /dev/sdb maj-min: 8:16 vendor: Samsung model: SSD 850 EVO 250GB size: 232.89 GiB block-size: physical: 512 B
logical: 512 B speed: 6.0 Gb/s type: SSD serial: <filter> rev: 2B6Q scheme: GPT
ID-5: /dev/sdc maj-min: 8:32 vendor: Samsung model: SSD 850 EVO 500GB size: 465.76 GiB block-size: physical: 512 B
logical: 512 B speed: 6.0 Gb/s type: SSD serial: <filter> rev: 2B6Q scheme: GPT
ID-6: /dev/sdd maj-min: 8:48 vendor: Toshiba model: HDWE160 size: 5.46 TiB block-size: physical: 4096 B
logical: 512 B speed: 6.0 Gb/s type: HDD rpm: 7200 serial: <filter> rev: FS2A scheme: GPT
Partition: ID-1: / raw-size: 896.79 GiB size: 896.79 GiB (100.00%) used: 202.84 GiB (22.6%) fs: btrfs dev: /dev/dm-0
maj-min: 254:0 mapped: luks-ced52dfa-6abb-4eed-8ed4-9015641e0caf
ID-2: /boot/efi raw-size: 300 MiB size: 299.4 MiB (99.80%) used: 700 KiB (0.2%) fs: vfat dev: /dev/nvme0n1p1
maj-min: 259:7
ID-3: /home raw-size: 896.79 GiB size: 896.79 GiB (100.00%) used: 202.84 GiB (22.6%) fs: btrfs dev: /dev/dm-0
maj-min: 254:0 mapped: luks-ced52dfa-6abb-4eed-8ed4-9015641e0caf
ID-4: /var/log raw-size: 896.79 GiB size: 896.79 GiB (100.00%) used: 202.84 GiB (22.6%) fs: btrfs dev: /dev/dm-0
maj-min: 254:0 mapped: luks-ced52dfa-6abb-4eed-8ed4-9015641e0caf
ID-5: /var/tmp raw-size: 896.79 GiB size: 896.79 GiB (100.00%) used: 202.84 GiB (22.6%) fs: btrfs dev: /dev/dm-0
maj-min: 254:0 mapped: luks-ced52dfa-6abb-4eed-8ed4-9015641e0caf
Swap: Kernel: swappiness: 133 (default 60) cache-pressure: 50 (default 100)
ID-1: swap-1 type: zram size: 31.29 GiB used: 0 KiB (0.0%) priority: 100 dev: /dev/zram0
ID-2: swap-2 type: partition size: 34.42 GiB used: 0 KiB (0.0%) priority: -2 dev: /dev/dm-1 maj-min: 254:1
mapped: luks-c1a24b17-8dee-48a9-8c22-95a63bbe0589
Sensors: System Temperatures: cpu: 34.0 C mobo: N/A gpu: nvidia temp: 45 C
Fan Speeds (RPM): N/A gpu: nvidia fan: 50%
Info: Processes: 312 Uptime: 19m wakeups: 0 Memory: 31.29 GiB used: 6.8 GiB (21.7%) Init: systemd v: 249 tool: systemctl
Compilers: gcc: 11.1.0 alt: 10 clang: 12.0.1 Packages: pacman: 1602 lib: 361 Shell: fish v: 3.3.1
running-in: alacritty inxi: 3.3.06