I'm productively using the 4er Kernel Image (25102019).
There the EMBUARY Skin works error-free.
YouTube I'm not using on the NanoPC-T4, I'm triggering it directly from TV.
Can you check and tell me which versions of Skin Helper Service & Skin Helper Service Widget addons installed on your system.
These two addons are what preventing custom skins on my v19 system.