Using Commit e95140ff433b805ca16df04cba501b7332a9ec95 I am able to duplicate.
NOTE: The Prolific detour appears to be a red-herring. It appears VENDOR ID 0x0c26 was used by ICOM in the past, however it may also be assigned to Prolific. I'm not sure if ICOM just sub-licensed the vendor ID, if it was a random assignment, or if the the vendor ID perhaps belong to another organization that Prolific bought.
https://the-sz.com/products/usbid/index.php?v=0x0c26 (random USB ID database)
http://www.linux-usb.org/usb.ids (Linux Kernel USB ID List)
0c26 Prolific Technology Inc.
0018 USB-Serial Controller [Icom Inc. OPC-478UC]
002b Icom Inc. IC-R30
Even though lsusb reports it is a Prolific device the kernel continues to use the FTDI driver.
Here are debug dumps from a RP2000V T and R ports, along with a RP2D port. Like the original poster I don't have access to spare systems either and these are in unknown condition (I'm told the 2000 had a bad TX amp and the RP2D was in working condition)
cmlara@donald:~/chirp$ ./venv/bin/python --version
Python 3.10.12
cmlara@donald:~/chirp$ sudo tools/icomsio.sh
Device ID-RP2000V TX is /dev/ttyUSB0 -> /dev/icom
cmlara@donald:~/chirp$ sudo ./venv/bin/python rpttool --debug /dev/ttyUSB0
Looking for a repeater...
DEBUG:chirp.drivers.idrp:Sending magic wakeup
DEBUG:chirp.drivers.idrp:Got:
000: fe fe 7f 01 19 29 25 01 .....)%.
008: 00 00 01 01 74 72 fd ....tr..
DEBUG:chirp.drivers.idrp:Sent 0 bytes, received 15
DEBUG:chirp.drivers.idrp:Got:
000: fe fe 7f 01 fb fd fe fe ........
008: 7f 01 19 29 25 01 00 00 ...)%...
016: 01 01 74 72 fd fe fe 7f ..tr....
024: 01 03 00 50 11 45 01 fd ...P.E..
032: fe fe 7f 01 1a 04 00 00 ........
040: fd fe fe 7f 01 1c 00 00 ........
048: fd fe fe 7f 01 1a 93 00 ........
056: 01 85 fd fe fe 7f 01 1a ........
064: 93 01 00 94 fd fe fe 7f ........
072: 01 1a 93 02 00 83 fd fe ........
080: fe 7f 01 1a 93 03 01 29 .......)
088: fd fe fe 7f 01 1a 93 04 ........
096: 01 fd fe fe 7f 01 1a 93 ........
104: 05 01 66 fd fe fe 7f 01 ..f.....
112: 1a 93 06 00 65 fd ....e...
DEBUG:chirp.drivers.idrp:Sent 0 bytes, received 118
DEBUG:chirp.drivers.idrp:Unhandled frame type 251
DEBUG:chirp.drivers.idrp:Unhandled frame type 25
DEBUG:chirp.drivers.idrp:Unhandled frame type 3
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 28
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
Unable to read memory from device: No frequency frame received
cmlara@donald:~/chirp$ lsusb
Bus 001 Device 012: ID 0c26:0012 Prolific Technology Inc. ID-RP2000V SERVICE T
cmlara@donald:~/chirp$ sudo tools/icomsio.sh
Device ID-RP2000V RX is /dev/ttyUSB0 -> /dev/icom
cmlara@donald:~/chirp$ sudo ./venv/bin/python rpttool --debug /dev/ttyUSB0
Looking for a repeater...
DEBUG:chirp.drivers.idrp:Sending magic wakeup
DEBUG:chirp.drivers.idrp:Got:
000: fe fe 7f 01 19 29 25 01 .....)%.
008: 00 00 01 01 74 72 fd ....tr..
DEBUG:chirp.drivers.idrp:Sent 0 bytes, received 15
DEBUG:chirp.drivers.idrp:Got:
000: fe fe 7f 01 fb fd fe fe ........
008: 7f 01 19 29 25 01 00 00 ...)%...
016: 01 01 74 72 fd fe fe 7f ..tr....
024: 01 03 00 50 51 44 01 fd ...PQD..
032: fe fe 7f 01 1a 04 00 00 ........
040: fd fe fe 7f 01 1c 00 00 ........
048: fd fe fe 7f 01 1a 93 00 ........
056: 01 86 fd fe fe 7f 01 1a ........
064: 93 01 00 94 fd fe fe 7f ........
072: 01 1a 93 02 00 59 fd fe .....Y..
080: fe 7f 01 1a 93 03 00 00 ........
088: fd fe fe 7f 01 1a 93 04 ........
096: 01 fd fe fe 7f 01 1a 93 ........
104: 05 01 15 fd fe fe 7f 01 ........
112: 1a 93 06 01 15 fd ........
DEBUG:chirp.drivers.idrp:Sent 0 bytes, received 118
DEBUG:chirp.drivers.idrp:Unhandled frame type 251
DEBUG:chirp.drivers.idrp:Unhandled frame type 25
DEBUG:chirp.drivers.idrp:Unhandled frame type 3
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 28
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
Unable to read memory from device: No frequency frame received
cmlara@donald:~/chirp$ lsusb
Bus 001 Device 013: ID 0c26:0013 Prolific Technology Inc. ID-RP2000V SERVICE R
cmlara@donald:~/chirp$ sudo tools/icomsio.sh
Device ID-RP2D is /dev/ttyUSB0 -> /dev/icom
cmlara@donald:~/chirp$ sudo ./venv/bin/python rpttool --debug /dev/icom
Looking for a repeater...
DEBUG:chirp.drivers.idrp:Sending magic wakeup
DEBUG:chirp.drivers.idrp:Got:
000: fe fe 7f 01 19 27 31 01 .....'1.
008: 00 00 01 01 74 56 fd ....tV..
DEBUG:chirp.drivers.idrp:Sent 0 bytes, received 15
DEBUG:chirp.drivers.idrp:Got:
000: fe fe 7f 01 fb fd fe fe ........
008: 7f 01 19 27 31 01 00 00 ...'1...
016: 01 01 74 56 fd fe fe 7f ..tV....
024: 01 03 00 00 50 99 12 fd ....P...
032: fe fe 7f 01 04 d1 01 fd ........
040: fe fe 7f 01 0c 00 00 00 ........
048: fd fe fe 7f 01 0f 10 fd ........
056: fe fe 7f 01 10 04 fd fe ........
064: fe 7f 01 16 4a 00 00 fd ....J...
072: fe fe 7f 01 14 0a 02 55 .......U
080: fd fe fe 7f 01 1a 04 00 ........
088: 00 fd fe fe 7f 01 1a 04 ........
096: 01 00 00 fd fe fe 7f 01 ........
104: 1a 05 04 00 fd fe fe 7f ........
112: 01 1c 00 00 fd ........
DEBUG:chirp.drivers.idrp:Sent 0 bytes, received 117
DEBUG:chirp.drivers.idrp:Unhandled frame type 251
DEBUG:chirp.drivers.idrp:Unhandled frame type 25
DEBUG:chirp.drivers.idrp:Unhandled frame type 3
DEBUG:chirp.drivers.idrp:Unhandled frame type 4
DEBUG:chirp.drivers.idrp:Unhandled frame type 12
DEBUG:chirp.drivers.idrp:Unhandled frame type 15
DEBUG:chirp.drivers.idrp:Unhandled frame type 16
DEBUG:chirp.drivers.idrp:Unhandled frame type 22
DEBUG:chirp.drivers.idrp:Unhandled frame type 20
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 26
DEBUG:chirp.drivers.idrp:Unhandled frame type 28
Unable to read memory from device: No frequency frame received