Linux Drivers for FT232R
Just asking: if you're not making a product, why don't just use something beginner-friendly (and very cheap)?
Let's say, an Arduino Nano clone is around $2, already has plenty of pins (D2-D13 + A0-A5, 2 left besides your 6+10, but you can extend that by a couple of 595s), and - after installing CH340G driver (built-in on Linux), you can use it as a virtual serial port. The PC side could be written in around 10 lines in Python, the Arduino side isn't hard either (just decode the input and display it by bitbanging the pins).

The only tricky part is the 150V power supply, but you can also get a PWM signal from the Arduino to drive a transformer (and A6-A7 left unused for a feedback).

(posted as answer as it's too long for a comment.. but it answers the implied XY-question)