Yes, you can do either with any bike.

For a derailleur setup, find an ancient derailleur for a cheap bike like an old Simplex. It may well have a steel hanger with the dropout slot on it. That's what you want. Now Simplex hanger is probably threaded wrong for a modern derailleur. You may be able to correct that with drill and taps. The adjusting screw stop will also be in the wrong location.

These hangers were made for many different bikes and derailleurs. I strongly suspect that locating one for say a late '70s Schwinn or any Japanese bike would have the correct threading and stop location. And you can also make one from 6061 aluminum plate. (I suspect finding a local machine shop to give you a scrap would be easy almost anywhere.) I did this many years ago and got a lot of use out it. You could make up a pattern from any modern bike's dropout and just cut it out. Biggest challenge would be the nut on the inside. (It will try to interfere with your cogs and may need to be recessed into the plate.) Not needed if you made it out of steel. Then you could just tap the hanger.

Most of the hangers have a screw behind the axle that goes into a fancy nut that fits inside the dropout slot to keep it located properly when the wheel is taken out, It is not essential, just nice. A threaded scrap of aluminum that jammed in the slot would work just fine.

Anyway - it's all doable.

And for an internal hub like a three speed? Find one with the correct dropout spacing. You do have to think about the geared hub must be nutted tightly enough to transfer the torque to the frame. In other words, dropouts of carbon fiber or soft aluminum may not be up to the job. Steel, no sweat. (A few weeks ago, someone posted about damaging a CF dropout this way. If you want to do this to a non-steel frame, look up that thread. There was some excellent advice there.)

Ben