[DjDiabolik]

When you add a youtube channel (from the add-on) as a favorite in Kodi, it does not update/refresh the video list. It will take some time to test since you need to add a channel, then wait for it to upload new videos, then access it from your favorite list again. This is not an issue (within the add-on) if you subscribe to the channel. I like to add channels I don't watch to often too favorites, so those videos doesn't "fill" up my subscription list.
If the plugin url is saved as plugin://plugin.video.youtube/user/xxxx, instead of plugin://plugin.video.youtube/channel/yyyy, things works as expected.
I'm guessing this is an issue with the value passed from the add-on to Kodi when the favorite is created. This worked as it should in the "old Bromix version".
CUT CUT

Apparently OSMC when you add a channel to favourites of Kodi from addons use the channelid instead the username........... i speak about this workaround how can you modify manually the favourites.xml and change the channelid whit username but this is not a good solution because in this case when you lauch the addons from favourites of kodi you obtain a result like a search result and not all video posted inside the channel, for obtain this you need to select a video... use the context menu and use the function "Go To (name of channel)".

Otherwise on youtube for some channel you can't obtain the username but some channel using only a channelid......... for this you need to use only the search function for obtain all video upload in this channel.........

Sorry again for my english...........

*EDIT*
I thinks the best solution it's make the add-on working more like the same recent on most recent Smart TV..... i have an LG SmartTV:
1) Lauch the youtube APP
2) Use the search engine
3) On result i can see all in one....... channel most relevant to my "search key", most relevant video this channel and if it's present all live stream from this channel etc etc but all it's be listening in all list

Actualy on this kodi add-on instead:
1) Lauch youtube add-on
2) Use the search engline
3) On result you need to select "Live" "Channel" and below you can obtain some video not exactly related to your "search key" used..........


If this youtube add-on can be adapter to working like recent smart tv app i thinks it's better because we can use only the search history feature and we can reach all channel directly after first search result......... also when you use search function by a browser on pc working in this mode.........