And who tells the server that the client hasn’t been modified
The server itself checks against what is allowed and what isn’t. It knows what the clients should be doing, and if they do something else it’s flagged. External hacks still, afaik, hook into the client and change the code as it is executed but still before it’s sent to the server, so you could still be checking against what the client is actually doing.
The external solution I mentioned in Blue Sentinel only exists because such a thing was not built into the game itself by FromSoftware, but there is no reason why it couldn’t be.
The server itself checks against what is allowed and what isn’t. It knows what the clients should be doing, and if they do something else it’s flagged. External hacks still, afaik, hook into the client and change the code as it is executed but still before it’s sent to the server, so you could still be checking against what the client is actually doing.
The external solution I mentioned in Blue Sentinel only exists because such a thing was not built into the game itself by FromSoftware, but there is no reason why it couldn’t be.