I have successfully installed a regular bike rack on my Swift in the past, but I have since removed it (just didn't use the bike that way anymore).

The basic rack will attach to the frame dropouts above the axle - there are holes there in standard size in the dropouts.

On the other end, I found the best solution was to use the bars that came with the rack, but instead of fitting them to a fixed point on the bike, I installed it on the shaft of the upper quick release. It worked fine. I think I trimmed up a couple of pieces of fuel hose to fit on each side, to keep it from moving.

It was sturdy and stable, and I carried panniers on it that way once, on a rough gravel track for several hours. No issues.

It will affect folded size, and does require disassembly for smallest fold. But if you just fold to get the bike into a car, you should still be ok.

Enjoy Spain!