low jitter

No, 200 to 500kHz is to much for a parallel port.
Also the step time and space at such a rate is to short for all cheap drives.
Parallel can do up to 50kHz if lucky with finding a PC, max i could do so far was around 70kHz.
Just in case, get a Mesa 5i25 or 6i25 or 7i92, those do 10MHz and have equivalent of 2 parallel ports, 34 pins and each can be an input or output.
Also, 7i80 has 4 parallel ports and can still be found.
Not very sure about the last one, so please do check.

Never tried, but i am pretty sure you can do raster with servo thread, it is updated 1000 times a second, should be enough.
I build small engravers/scratchers that use PWM to control head pressure, with parallel port, but the max speed is 3 meters per minute, so even 100000ns base period is enough.
I wonder why would you need 500kHz?
An old Fujitsu-Siemens workstation did 70kHz, it was a dual 4 core Xeon, it died! Later found out the 700W power supply had dry capacitors.

Almost forgot, some Mesa boards can easily do 250000ns servo period, so that is 4000 updates per second.

I think that HAL_PORT is in 2.9 but some new laser-related content has only gone in to master (and only just now, as I was waiting for CI to check it, and then git distracted)

github.com/LinuxCNC/linuxcnc/pull/2171