Here is a copy of part of the reply I sent to vandys privately, the result of the Ubuntu attempt, in case someone else wants to chime in:

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ubuntu@ubuntu:~$ cd Downloads
ubuntu@ubuntu:~/Downloads$ dir
flasher-3.0-static
ubuntu@ubuntu:~/Downloads$ chmod a+x flasher-3.0-static
ubuntu@ubuntu:~/Downloads$ sudo rmmod cdc_phonet
Error: Module cdc_phonet is not currently loaded
ubuntu@ubuntu:~/Downloads$ sudo rmmod phonet
Error: Module phonet is not currently loaded
ubuntu@ubuntu:~/Downloads$ sudo ./flasher-3.0-static -f -F RX-44_DIABLO_5.2008.43-7_PR_COMBINED_MR0_ARM.bin -R
flasher v0.9.0 (Jan 19 2007)

SW version in image: RX-44_DIABLO_5.2008.43-7_PR_MR0
Image 'kernel', size 1536640 bytes
Version 2.6.21-200842maemo1
Image 'initfs', size 2327808 bytes
Version 0.95.22-200842maemo1w38b3
Image 'rootfs', size 125435904 bytes
Version RX-34+RX-44+RX-48_DIABLO_5.2008.43-7_PR_MR0
Image '2nd', size 8192 bytes
Valid for RX-44: 0808
Version 1.1.16-200844maemo2
Image 'xloader', size 9216 bytes
Valid for RX-44: 0808
Version 1.1.16-200844maemo2
Image 'secondary', size 100736 bytes
Valid for RX-44: 0808
Version 1.1.16-200844maemo2
Image '2nd', size 8192 bytes
Valid for RX-44: 0801, 0802, 0803, 0804, 0805, 0806, 0901, 0902
Version 1.1.16-200844maemo2
Image 'xloader', size 9216 bytes
Valid for RX-44: 0801, 0802, 0803, 0804, 0805, 0806, 0901, 0902
Version 1.1.16-200844maemo2
Image 'secondary', size 100736 bytes
Valid for RX-44: 0801, 0802, 0803, 0804, 0805, 0806, 0901, 0902
Version 1.1.16-200844maemo2
Suitable USB device not found, waiting
USB device found found at bus 001, device address 006
Error claiming USB interface: Device or resource busy

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If it helps, the Windows attempt was obtained from a different computer than the Ubuntu attempt.

Thanks to everyone for all the help so far.