Hmm, interesting, I tried on a brand new machine, and indeed I got the same thing:
Running SteamCMD
- Executable: C:\DSL\DedicatedServerLauncher\steamcmd.exe
- Parameters: +login anonymous +force_install_dir "C:\DSL\DedicatedServerLauncher\ConanExilesDedicatedServer" +app_update 443030 -beta default +quit
----- Started Tue 06/08/2021 12:02:40.03 -----
Redirecting stderr to 'C:\DSL\DedicatedServerLauncher\logs\stderr.txt'
[ 0%] Checking for available updates...
[----] Verifying installation...
Steam Console Client (c) Valve Corporation
-- type 'quit' to exit --
Loading Steam API...OK.
Connecting anonymously to Steam Public...Logged in OK
Waiting for user info...OK
ERROR! Failed to install app '443030' (Disk write failure)
----- Finished Tue 06/08/2021 12:02:43.31 with status code 8 -----
Waiting for 3 seconds, press a key to continue ...
What exactly did you enter as command parameters?