XXLRay
I Love YTtalk
I made a a collaboration video with another channel some time ago. Just recently I put their channel name into the tag section and this is the result for that video:

It's forbidden to do this with unrelated channel names but as this is a collaboration video I guess the tag is still relevant.
Note that not only the traffic from suggested videos did pick up but also the one from cards and annotations. I have no idea why the latter one is the case.
Their video has 700k+ views by the way. I somehow got lucky as their next most watched video has "only" 30k+ views.
So if I learned something from this then it is that linking each other in annotations and cards isn't necessarily sufficient to get into the recommendation section but that tags can be the break through.

It's forbidden to do this with unrelated channel names but as this is a collaboration video I guess the tag is still relevant.
Note that not only the traffic from suggested videos did pick up but also the one from cards and annotations. I have no idea why the latter one is the case.
Their video has 700k+ views by the way. I somehow got lucky as their next most watched video has "only" 30k+ views.
So if I learned something from this then it is that linking each other in annotations and cards isn't necessarily sufficient to get into the recommendation section but that tags can be the break through.