I faced exactly the same error as seen here. Here it is in full:

Error detected while processing /home/*********/.config/nvim/init.lua:

E5113: Error while calling lua chunk: /home/*********/.config/nvim/lua/core/init

.lua:6: attempt to call local 'autocmd' (a nil value)

stack traceback:

/home/*********/.config/nvim/lua/core/init.lua:6: in main chunk

[C]: in function 'require'

/home/*********/.config/nvim/init.lua:7: in main chunk

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Scenario

A debian distro
Attempting to install & run NvChad
NvChad has a few simple pre-requisites: certain type of font, neovim (hint, this is where the issue was)
Font was installed properly, I love Jetbrains Mono, so I went with that as per.
nvim however, was version 0.6.*, installed via apt. NvChad’s lua files need nvim 0.9.*

Solution

The fix was installing nvim directly from the repo using curl. It’s distributed as an AppImage ("universal" Linux package) which promise to run on most linux systems.

fix for - attempt to call local autocmd (a nil value)

Scenario

Solution