HP laptop: RTL8822CE WiFi sometimes fails for no reason

Question

On my brand new HP laptop the WiFi connection suddenly fails for no particular reason. Available networks are displayed, but attempting a connection never succeeds. This has happened twice now since I bought the machine about a month ago. My other machines and the telephone connect fine, so I know the network is healthy. And yes, I use the correct password. Network secured by WPA2.

lspci |grep Net gives

01:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8822CE 802.11ac PCIe Wireless Network Adapter

I have tried to restart the network driver (sudo systemctl restart NetworkManager.service, or by using the GUI), without any success.

Unfortunately, the only solution seems to be a complete restart of the machine. That always works, but why?? I hate rebooting, should not be necessary for a stable system. The machine is always on, but is suspended every might.

Right NOW it's OK of course – I'm writing this on it. I would love to have other things to try the next time this happens. Maybe look at something in /var/log? sudo dmesg doesn't make me wiser. rfkill reports no blocking.

Note also that there is no Windows on this machine; I cleared the disk and installed Ubuntu 20.10 first thing when I bought it :)

Addition, after some valuable input here:

I have now looked at the journals, sudo journalctl -b X -u NetworkManager where X is either 0 or -1 to select last or previous boot. Output from journalctl is quite large, and with very long lines not readable here in any case. Including the whole file is not feasible, and a link to the file on my local machine cannot be done. If someone thinks the log could contain useful information, and could also give me a hint on how to publish a 50kb file here, please do :)

Some warnings I spotted that might be related:

Apr 13 19:16:25 linn NetworkManager[590]: <warn>  [1618334185.4874] ifupdown: interfaces file /etc/network/interfaces doesn't exist
Apr 13 19:16:26 linn NetworkManager[590]: <warn>  [1618334186.4560] Error: failed to open /run/network/ifstate