Invitations weren't working for me until I added 'nocanon' to these additional places. Until then, invitations failed with "Invalid signature for server ..." errors, as in https://github.com/matrix-org/synapse/issues/3294 .
I didn't check whether the user_directory/search proxy line also needs it, I just assumed it should have it too.
The other two proxy lines in this example also include a 'retry=0' parameter. That's a separate issue; I haven't touched it here.
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