How in heart is possible to work with a router that randomly shutdowns itself around 3/4 times a day without any reason. Leaving me without internet for 10-15 minutes. I called my ISP and they said that they don't see any problem and they will not send any replacement. I can instead fix an appointment with their technician to have a look at the issue, but of couse, I'm paying for him.

How about no? I'm going to buy a proper modem/router next month, this shit router they give you have 1/100 of the proper configurations options you need.

Had the same issue to be fair. In my parents house we had a provider which gave us a router and well... It disconnected with no reason... Ping jumps were insane (literally unstable). Tried to call them over 20 times, no luck. In the end we asked them to come with their paid technician that we agreed to pay ONLY if he finds no issues. They hesitated but sent one out. (well, their data showed that all was ok...).

In the end, technician found out that our router was ultra defective within 2 minutes and more on that - found that our distribution box was faulty too. They replaced both of them and.... Issue was somewhat gone. Except... new router didn't really work on wifi...

Years later - no luck from them. Technicians don't even come to our place anymore :)

This is why I bought my own router and modem.

Well, it was mostly because Comcast router/modem combos come with a public wifi Hotspot enabled by default and I'm not letting other people leech my bandwidth.