Well… qemu supports a few models, and apparently `ne2k_isa` is one of them -- probably your best bet with an early 90s vintage OS.
`qemu-system-i386 -net model=ne2k_isa,irq=5,iobase=0x280 …` from what I gather via a quick search on the topic.
Failing that, maybe SLIP or PPP via a virtual serial port mapped to a pseudo TTY.