Fanout scenario with dotnet driver

[troepolik]

Hi! I tried to implement fanout scenario with one of the kafka topics.
The recommended way is to set consumer group id = ""
But it does not work with dot net driver.
If I set GroupId to "" I get error
"Failed to redirect the poll queue to consumer_poll queue: Local: Unknown group'"
If I set GroupId to null I get error
"'group.id' configuration parameter is required and was not specified."

Am I doing something wrong? Or may be this is not supported by reason?

The alternative way is to specify uniq consumer group for each consumer by generating GUID.
But this way was less recommended.
And I have some concerns about this way because each time any app pod will be restarted the new consumer group will be created on kafka side. Won't we have any problem with high amount of old consumer groups in future?