Does anyone know if an Avast VPN can be used directly through my router and not individually through single computers?
My vote is no.
however I could be 100% wrong 8)
Great answer, Thanks. It’s 50/50 and I’m 100% sure of that.
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No, you cannot do that. 
The only way to use SecureLine is by using their apps. You don’t have the freedom to choose between another OpenVPN apps around the internet.
So, you cannot even connect it through your router.
I fully understand. Thank you for the info!!!