The mod Kuxynator's Smart Linked Chests (3.0.16) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Kux-SmartLinkedChests::on_nth_tick(1)
Unknown entity name: smart-linked-surface-chest
stack traceback:
[C]: in function 'find_entities_filtered'
Kux-SmartLinkedChests/modules/Chest.lua:551: in function 'rescan'
Kux-SmartLinkedChests/modules/Chest.lua:609: in function 'rescan'
Kux-SmartLinkedChests/modules/Chest.lua:617: in function 'fnc'
Kux-CoreLib/lib/EventDistributor.lua:175: in function 'fnc'
Kux-CoreLib/lib/EventDistributor.lua:146: in function <Kux-CoreLib/lib/EventDistributor.lua:142>

What are your mod settings?

https://i.imgur.com/TxRHIIC.png
https://i.imgur.com/J7C49Fe.png

I have determined though that changing any of the "Enable Smart Linked" chest options bricks the game with that unrecoverable error. This worked fine in Factorio 1.1.x

Turns out you can't just blindly scan for ALL 4 internal chest names anymore. Factorio 1.1 just silently returns an empty result for find_entities_filtered with invalid entity names. Factorio 2.0 explicitly throws an error for that same action.

no one had ever deactivated the chests before ;-)
fixed in next update