I just set up a Dell Optiplex with Pentium I and Win98 for work in a research lab. We had an old Varian Cary 50 UV-vis spectrophotometer that would only interface via proprietary ISA card, and has proprietary drivers that are probably not compatible with newer versions of Windows.

Debugging was funny. The thing mostly worked right after install, but two of the proprietary software apps would freeze the whole system on launch. It turned out that they needed at least 800x600 graphics, and I was stuck in 640x480 using a universal graphics driver. I found a proper graphics driver for the video card (had to download on one computer, burn CD on a second computer, and then put the CD into the old Dell) and installed it, increased the resolution to a whopping 1024x768, and hey presto it worked!

Apparently you can get modern motherboards with ISA slots, manufactured mainly for the defense and science markets, because they use a lot of legacy hardware. Unfortunately, biological science budgets have been slashed due to covid-19 unless you're working on a project that is absolutely related (robbing peter to pay the piper or some other unattractive mix of metaphors) which is why I'm stuck with this old system. On the plus side, I found it kind of fun.