My method for disabling all mods is renaming
This stops BepInEx cold in its tracks because it doesn't even get injected into the valheim.exe process anymore => completely disables BepInEx.

(in Linux - just don't use BepInEx's start script...)

Originally posted by Wafflesaurus Supreme:

Rename the plugins folder.

This leaves one mod running - BepInEx!

Originally posted by AlexSledge:

Rename: E:\SteamLibrary\steamapps\common\Valheim\doorstop_config.ini to .bak
Now BepInEx won't get loaded, this no mods loaded.

I think this has the same problem as above - BepInEx still gets injected at runtime and if your BepInEx itself is too old / not compatible anymore it still might interfere with VH.