Error: Could not find USBtiny device

Hello - I'm trying to upload sketch to an Adafruit Trinket board and I keep getting the error above. Tried on both Windows, Mac and Linux - same deal :-(((

Arduino IDE is 1.8.12, Board set to Trinket, programmer is USBTiny. The board is connected and has one green LED and a changing color cone. At least in Linux I can verify it is connected:

[ 1545.492897] usb 1-3: new full-speed USB device number 9 using xhci_hcd
[ 1545.642821] usb 1-3: New USB device found, idVendor=239a, idProduct=801f
[ 1545.642826] usb 1-3: New USB device strings: Mfr=2, Product=3, SerialNumber=1
[ 1545.642829] usb 1-3: Product: Trinket M0
[ 1545.642832] usb 1-3: Manufacturer: Adafruit Industries LLC
[ 1545.642835] usb 1-3: SerialNumber: A14C93AC933415050213E223B22201FF
[ 1545.644123] cdc_acm 1-3:1.0: ttyACM0: USB ACM device
[ 1545.645368] usb-storage 1-3:1.2: USB Mass Storage device detected
[ 1545.645866] scsi host6: usb-storage 1-3:1.2
[ 1545.648364] input: Adafruit Industries LLC Trinket M0 as /devices/pci0000:00/0000:00:14.0/usb1/1-3/1-3:1.3/0003:239A:801F.000A/input/input22
[ 1545.706258] hid-generic 0003:239A:801F.000A: input,hidraw6: USB HID v1.11 Keyboard [Adafruit Industries LLC Trinket M0] on usb-0000:00:14.0-3/input3
[ 1546.669713] scsi 6:0:0:0: Direct-Access                                    PQ: 0 ANSI: 3
[ 1546.670247] scsi 6:0:0:1: Direct-Access                                    PQ: 0 ANSI: 3
[ 1546.671240] sd 6:0:0:0: Attached scsi generic sg2 type 0
[ 1546.671835] sd 6:0:0:0: [sdc] 129 512-byte logical blocks: (66.0 kB/64.5 KiB)
[ 1546.671895] sd 6:0:0:1: Attached scsi generic sg3 type 0
[ 1546.672099] sd 6:0:0:0: [sdc] Write Protect is off
[ 1546.672103] sd 6:0:0:0: [sdc] Mode Sense: 00 00 00 00
[ 1546.672703] sd 6:0:0:0: [sdc] Asking for cache data failed
[ 1546.672711] sd 6:0:0:0: [sdc] Assuming drive cache: write through
[ 1546.673430] sd 6:0:0:1: [sdd] Attached SCSI removable disk
[ 1546.682858]  sdc: sdc1
[ 1546.684787] sd 6:0:0:0: [sdc] Attached SCSI removable disk

The port selected is /dev/ttyACM0. When I select "Board Info" in the IDE, it seems to find it and detect at least some of the IDs:

BN: Unknown board
VID: 239A
PID: 801F
SN: Upload any sketch to obtain it

However when I try to upload, I get:

/home/username/devel/arduino-1.8.12/hardware/tools/avr/bin/avrdude -C/home/username/devel/arduino-1.8.12/hardware/tools/avr/etc/avrdude.conf -v -pattiny85 -cusbtiny -Uflash:w:/tmp/arduino_build_865286/TrinketPlayer.ino.hex:i 

avrdude: Version 6.3-20190619
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "/home/username/devel/arduino-1.8.12/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/home/username/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : usb
         Using Programmer              : usbtiny
avrdude: Error: Could not find USBtiny device (0x1781/0xc9f)

avrdude done.  Thank you.

the selected serial port 
 does not exist or your board is not connected

Am I missing something in the way I set it up? Any help would be greatly appreciated!

Update: OK, it seems to be a bootloader problem. Trinket is supposed to signal the bootloader readiness by flashing red LED, which I don't get (tried two different cables, which curiously give me different results: one shows the glowing changing color LED mentioned before, the other gives a solid purple light from the same LED). Possibly a board problem?