Solution: I followed this comment https://lemmy.world/comment/17771097 and changed the Proton version from 9.0-4 to 8.0-5

I’m using Proton 9.0.4 to run the game. It used to run without errors, I don’t know what changed.

steam logs when trying to run the game

wine: using kernel write watches, use_kernel_writewatch 1.
fsync: up and running.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
chdir "/home/dope_ass_pc/.local/share/Steam/steamapps/common/rocketleague/Binaries/Win64"
Game Recording - would start recording game 252950, but recording for this game is disabled
Adding process 52754 for gameID 252950
ERROR: ld.so: object '/home/dope_ass_pc/.local/share/Steam/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored.
wine: using kernel write watches, use_kernel_writewatch 1.
fsync: up and running.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
wine: using kernel write watches, use_kernel_writewatch 1.
Setting breakpad minidump AppID = 252950
Steam_SetMinidumpSteamID:  Caching Steam ID:  76561198029811659 [API loaded no]
wine: using kernel write watches, use_kernel_writewatch 1.
06/19 19:49:08 minidumps folder is set to /tmp/dumps
Game Recording - game stopped [gameid=252950]
Removing process 52754 for gameID 252950

fasfetch info

OS: Arch Linux x86_64
Host: Nitro AN517-54 (V1.20)
Kernel: Linux 6.15.2-arch1-1
Uptime: 4 hours, 8 mins
Packages: 1267 (pacman), 17 (flatpak)
Shell: zsh 5.9
Display (eDP-1): 1920x1080 @ 60 Hz in 17" [Built-in]
DE: KDE Plasma 6.3.5
WM: KWin (Wayland)
WM Theme: Breeze
Theme: Breeze (Dark) [Qt], Breeze-Dark [GTK2], Breeze [GTK3]
Icons: breeze-dark [Qt], breeze-dark [GTK2/3/4]
Font: Noto Sans (10pt) [Qt], Noto Sans (10pt) [GTK2/3/4]
Cursor: breeze (24px)
Terminal: konsole 25.4.2
CPU: 11th Gen Intel(R) Core(TM) i5-11400H (12) @ 4.50 GHz
GPU 1: NVIDIA GeForce RTX 3050 Mobile [Discrete]
GPU 2: Intel UHD Graphics @ 1.45 GHz [Integrated]
Memory: 5.78 GiB / 15.39 GiB (38%)
Swap: 606.31 MiB / 16.94 GiB (3%)
Disk (/): 306.03 GiB / 450.71 GiB (68%) - ext4
Disk (/mnt/ssd): 309.28 GiB / 439.04 GiB (70%) - ext4
Battery (AP18E7M): 95% [Charging, AC Connected]
Locale: en_US.UTF-8