How to tell ModemManager to ignore some or all of tttyUSB*?

I want to tell ModemManager to leave my Tungsten E (Palm Pilot) alone. I’m running Ubuntu 16.04.6 LTS

My logs tell me:

Jul 30 22:00:41 bat kernel: usb 1-1.1: new full-speed USB device number 29 using ehci-pci Jul 30 22:00:41 bat kernel: usb 1-1.1: New USB device found, idVendor=0830, idProduct=0060 Jul 30 22:00:41 bat kernel: usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=5 Jul 30 22:00:41 bat kernel: usb 1-1.1: Product: Palm Handheld Jul 30 22:00:41 bat kernel: usb 1-1.1: Manufacturer: Palm, Inc. Jul 30 22:00:41 bat kernel: usb 1-1.1: SerialNumber: PalmSN12345678 Jul 30 22:00:41 bat kernel: visor 1-1.1:1.0: Handspring Visor / Palm OS converter detected Jul 30 22:00:41 bat kernel: usb 1-1.1: Handspring Visor / Palm OS converter now attached to ttyUSB0 Jul 30 22:00:41 bat kernel: usb 1-1.1: Handspring Visor / Palm OS converter now attached to ttyUSB1 Jul 30 22:00:41 bat mtp-probe[5886]: checking bus 1, device 29: "/sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.1" Jul 30 22:00:41 bat mtp-probe[5886]: bus: 1, device: 29 was not an MTP device Jul 30 22:00:43 bat snapd[1623]: hotplug.go:193: hotplug device add event ignored, enable experimental.hotplug Jul 30 22:00:43 bat snapd[1623]: hotplug.go:193: hotplug device add event ignored, enable experimental.hotplug Jul 30 22:00:45 bat ModemManager[1303]: <warn>  (ttyUSB1): port attributes not fully set Jul 30 22:00:45 bat ModemManager[1303]: <warn>  (ttyUSB0): port attributes not fully set Jul 30 22:01:27 bat ModemManager[1303]: <warn>  (ttyUSB0): close blocked by driver for more than 7 seconds! Jul 30 22:01:33 bat ModemManager[1303]: <info>  Creating modem with plugin 'Generic' and '2' ports Jul 30 22:01:33 bat ModemManager[1303]: <warn>  Could not grab port (tty/ttyUSB1): 'Cannot add port 'tty/ttyUSB1', unhandled seria Jul 30 22:01:33 bat ModemManager[1303]: <warn>  Could not grab port (tty/ttyUSB0): 'Cannot add port 'tty/ttyUSB0', unhandled seria Jul 30 22:01:33 bat ModemManager[1303]: <warn>  Couldn't create modem for device at '/sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1 Jul 30 22:02:04 bat ModemManager[1303]: <warn>  (ttyUSB0): close blocked by driver for more than 7 seconds! 

I want to prevent ModemManager from trying anything with /dev/tty/ttyUSB[01] or even /dev/tty/ttyUSB*.