Short of getting a USB PCMCIA card and a midisport uno you could try to build a serial port midi adapter, but you would need a driver too that maps the midi to the serial port. Or someway to adapt the serial port for usb devices.
For software There's All Sound Tracker. That will take midi input and can use OPL3.
I think there may even be mpu-401 pcmcia cards,
but people have been buying up all the old pcmcia cards, hard to find much these days.
Best to find some way to add usb.

Forgive my ignorance as I'm still getting familiarized with the ins and outs of older hardware.

Been trying to rig together a Pure Data/OPL 3 setup. Specifically, I have a bunch of weird generative midi patches in pure data, and I want to send the midi out to an OPL3 laptop triggering samples (could be through impulse tracker midi-in, openmpt, etc.)

I have a Libretto 50CT with a port replicator which offers these connections: https://imgur.com/a/a6ZuVtt

None of these connect to the MPU-401 midi interface inside, right? I've heard of people soldering directly to the MPU-401 chip but I don't know if I feel comfortable taking a soldering iron to this thing.

As an alternative, are there cheaper opl3 laptops (like a tecra 8000) that have a simpler midi-in option? Maybe someone can shed some light on how midi control input works on opl3 laptops in general.

Love u guys