@bubleponge 

This is the line that tells Main Deco loses connection, ignore the rest:

Mon Aug 9 12:34:07 2021 daemon.notice conn-indicator: Connectivity changed: ONLINE(0x0) -> OFFLINE(0x1)

It will be followed by log line having "Connectivity changed: OFFLINE(0x1) -> ONLINE(0x0)" in it. Find it in your log and you'll have end of the outage and its duration.

By just Deco logs you won't be able to figure where the problem is. Deco will report it loses Internet connection, but also that could just mean it couldn't resove host names, meaning DNS server issues.

What sort of ISP router do you have, is it cable modem, fiber, something else? Can you login to ISP router to check WAN and LAN connectivity uptime? I have HITRON CODA-4582, it is cable roter/modem and it provides that info. Very rudimental, just says when Internet connection was interrupted last time, no duration or history, but that is enough.

I also experienced intemittent Internet interruptions every day, and ISP suport denied it were their issues. They said nobody else complained in my area. Finally, they sent technician who found cable, coming into my house, with cracked insulation. When quality of signal went below acceptable level, HITRON rebooted itself as part of automatic troubleshooting, and that terminated my Internet during the reboot. Technician replaced cable, problem solved. 

In my case, internet cutouts were happening at different times of day and night, but were of the same duration, because ISP router always takes the same time to reboot itself. That might be a hint for you, too, if interruptions happen randomly but of the same short time every time, according to Deco logs.

I collected times when Internet went down, and because they were indeed random, and at day and night, that helped to have meanigful conversation with IT support from my ISP.

It is obvious that while Internet connection could go down once in a while at night (ISP maintenance) or during the day (technician fixes someone's else Internet in your area and accidentally brefly knocks down yours), having daily accourence of internet interruptions at random times is something else.