I've been getting e-mail help from TP-Link's Sandy Wei, but I wanted to share here.

A few problems:
1) Originally, occasional internet drops that corrected on their own
2) The log isn't really been helpful for debugging, e.g. it doesn't show anything around the time of the drops
3) 221128 firmware seems worse than 220221, dropping internet daily and requiring reboots to fix
4) Time is not correct on boot

History:
AX11000 v1.6 installed in March, 2022
I had been on firmware 220221 (I think) until about 2 weeks ago, then 221128, then back.

In Q4-2022 I was having occasional internet drop-outs between 10-2 in the evening, but they recovered on their own. I'd get infrequent complaints from my son and notifications from my Flume, or experience it myself.

A flurry of these drops in mid-January prompted me to login to the router, which indicated a firmware update (221128) was available, so I installed it. In parallel I contacted tech support. Further troubleshooting demonstrated that both wifi and wired lose the ability to reach the internet. The AX11000 can still be reached locally via its web portal or Tether app. Status from the AX11000 indicates poor connection or disconnected. The cable modem appears to be fine. After I changed the MAC address on my AX11000 to match my laptop, I was able to prove that the the cable modem still had an internet connection when the AX11000 drops.

Upgrading to FW 221128 seemed to exacerbate the internet drops. They started happening ~daily and required reboots to fix. A couple of times they occurred soon after work Zoom/Teams calls in the morning, but this isn't necessarily repeatable.

Switching back to 220221 FW seems to have resolved the daily drops. I haven't had a problem in 4 days.

Along the way I noticed the time in the log - after a reboot - was wrong:
    2022-02-21 00:00:16 remote-management[6534]: <6> 282505 Service stop
then adjusted to the proper time during the boot process
    2023-01-31 10:46:46 traffic-stats[8964]: <6> 269001 Clear all stats because time changed
I thought this was an issue with the upgrade to FW 221128, because when I re-ran a quick start setup on it, it had the wrong time zone. Correcting that got rid of the time problem in the log. But after going back to FW 220221, I can't get rid of the time bug even with the correct time zone setting.

I've got a replacement AX11000 on the way, but I'm thinking this may be a combination of a hardware problem and firmware sensitivity.