Getting Toshiba VF-S11 VFD to communicate over cheap RS485 to USB dongle

Hello,
first of all, i am sorry for creating the 3. thread within a short time, but i think its better to ask that in a new thread than in this one:
Toshiba VF-S11 VFD for Lathe Spindle - Problems with setup/wiring to 7i76e

Before my Mesa 7i76e out put driver burned out (yesterday) i got my VFD to work (almost properly) with the help of PCW.
I would need to scale the 0-10V analog signal in Linuxcnc to get the correct RPM, but i know from my CNC Router (with Huanyang VFD) that the MODBUS communication/control might be the best way to control a spindle, or at least i did not need to do any scaling and it works perfectly.

In the thread "Toshiba VF-S11 VFD for Lathe Spindle - Problems with setup/wiring to 7i76e" Thread, i wrote that i think i need the "Toshiba USB-to-Serial Conversion Unit (model: USB001Z)" to control the vfd via modbus, so i thought i will just use the 0-10V analog communication .
That conversion unit costs about 110€, which is a lot more than the cheap RS485 to USB dongles, which are working well, so i started to look for a solution.
I found a interesing discussion which is difficult to read due to strange forum format : Sourceforge [Emc-users] VFS-11 modbus driver
Actually i dont understand much, just that that i might be possible to control the vfd with a cheaper dongle than the original USB-to-Serial Conversion Unit.

Could please anyone tell me if its possible? I really tried to find it out by my self, but its not that easy for someone with not much knowledge about those things.

I found also some RJ45 and RS232 connection diagrams from the VFD:
wiki.linuxcnc.org/uploads/VFS11-RJ45_e.pdf
static.mah.priv.at/cnc/vfs11-rs232.pdf

If it would be possible to get to know who wrote the Linux Toshiba VF-S11 driver (linuxcnc.org/docs/html/drivers/vfs11.html), then i would really like to contact that person. Maybe he/she can give me some informations.

Thanks in advance.