Posted her because I've notice the exact same thing on my MB Pro. Fully updated OS, fully updated Avast, but after MBP has been asleep, when it wakes up there is zero internet connection through Chrome or Safari. Anyone else with this?
Only way I could get network working again was to disable the anti-tracking privacy thing, then my connection miraculously returned. Checking now, it looks like it has switched itself back on, but my connection is still fine. Weird. Oh no, it had turned itself back on, and my connection was dead again. So it is definitely Avast Anti-Track that's blocking everything.
Update: read another post and looked for extension conflicts. Only two there were for Avast:
* * 6H4HRTU5E3 com.avast.osx.secureline.networkextension (4.2.5/48920) Avast Smart VPN Network Extension [activated enabled]
* * 6H4HRTU5E3 com.avast.Antivirus.SystemExtension (1.3.90/1.3.90) Avast Antivirus System Extension [activated enabled]