@MrT10001 Yes. I rebooted many times. Two Ubuntu Desktops, three USB cables, toggled Developer Mode, dmesg registers nothing with my UT phone, unless in Recovery Mode. That's the only situation where the USB cable and ADB works. It seems something in the UT OS has disabled MTP.
Later today I found this posting:
https://forums.ubports.com/topic/8849/mtp-not-working-on-pixel-3a-xl-after-ota-25-update
It appears to be a recent issue with UT OTA-25.
Thank you for any assistance you can offer.