I don't understand something by namespaces.
It's kind of
$wgNamespaceContentModels [NS_TALK] = 'flow-board';
$wgNamespaceContentModels [NS_USER_TALK] = 'flow-board';
configured in the config,
but there is no sense, it still gives an error
Fail to create title from namespace 2600 and title text 'w9wvzwvqp5gb5efg'
And judging by the info from MW (https://www.mediawiki.org/wiki/Extension_default_namespaces) - 2600 is just from him NameSpace.
It seems to me that you just need to add something correct in the config. Distribute roofing felts, declare namespace roofing felts.
Can someone help with this?