Hi Vasilis,
Sorry for the confusion here, but MySQL Cluster replication currently requires that only the *default*, unnamed channel is used for replication.
This channel is described here :
https://dev.mysql.com/doc/refman/8.0/en/replication-channels.html
https://dev.mysql.com/doc/refman/8.0/en/channels-with-prev-replication.html
The output above shows that you have a single named channel (my_channel_1), and also a (hidden) default channel, for a total channel count of 2 - this is why MySQL Cluster is not replicating.
I can see that this is confusing and has caused you to waste time trying to get replication started, so we should look at lifting this restriction in some way, but in the meantime, you need to get rid of the named channel and use the default channel to get MySQL Cluster replication to work.
Good luck,
Frazer