Season 6 is available for streaming through the following service:

 
 
 
Amazon Freevee (formerly IMDb TV) / Amazon Prime Video
 

From 03/01/2022 on, all episodes of the series (seasons 1 through 9) can be watched for free through this streaming service, which is exclusively available for people with a U.S. IP address and a residential address in the U.S. Due to geo-blocking, streaming is not available for customers outside the U.S.
The quality is much better than in TV airings, but varies from episode to episode. No picture remastering was applied, so the picture quality is not as good as the season 3 DVD release.
All season 6 episodes are unedited.
 
There is no information available at this time if and when Amazon will be streaming the series in Europe.