Network suddenly disconnects (Dell XPS laptop)

I have an issue on a Dell XPS 15 laptop where the network connection suddenly disconnects.

What I’ve found is that after 5-10 minutes after logging into the desktop and working on it, the network suddenly fails, so that when I ping for instance the response is “Destination Host Unreachable”.
I switched from NetworkManager to dhcpcd, but I’m having the exact same problem with both.
Checking the logs for dhcpcd I found that it said “DCHP lease expired” and then “No ipv6 routes”.
After suffering the disconnect I checked ip route and there were no routes anymore.

Any idea what could cause this behavior? I haven’t changed any settings for neither NetworkManager or dhcpcd.
Could this have anything to do with my home router hardware? I have an ASUS RT-AC66U which is about 7 years old.
What should I check to further investigate?

Here are my journalctl logs from a session, from boot until just after the network breakage:

You could use eos-log-tool to produce logs when the error has occurred.
The inxi log shows your hardware.

Have you updated your router’s firmware?

Yes, my router is up to date, but I still think it’s the culprit.
I’ve tried a separate network cable, and I keep getting the carrier lost message in the logs.
So I decided to just throw money at the problem and will be replacing my Asus router with some more proper gear from Ubiquiti. Not only due to this issue, but also because I’ve been having lackluster wifi connectivity lately as well, so I suspect that the Asus router, being about 7 years old, is probably getting tired.

It is possible that ac66u is no more supported.
The latest firmware seems to be from February 5th, 2021. After that date there have been a few important security updates on other Asus routers.

The WiFi chip is also using ath11_pci which is very new so there may be some issues because the router is older.

Network: Device-1: Qualcomm QCA6390 Wireless Network Adapter [AX500-DBS ] vendor: Rivet Networks driver: ath11k_pci
v: kernel port: 3000 bus-ID: 6c:00.0 chip-ID: 17cb:1101 class-ID: 0280

Jun 19 16:22:28 arch kernel: ath11k_pci 0000:6c:00.0: WARNING: ath11k PCI support is experimental!

The QCA6390 supports the latest AX standard so hopefully you get a router that supports that.
I also provide some other information just for your perusal.

Edit: Also have a look here.