Services->System, backup, Configure. Under "Type" select "Dir". Read the tooltips and the Online Help (blue (?) icon).
imagemagic is not available for Alt-F.
You can just define a network share and make the thumbnails in another computer using your prefered programs.
Or you can try install "ffmpegthumbnailer" (Packages-> Alt-F) and evaluate it. It is intended to generate video files thumbnails, but it worked for me on a plain jpg file:
ffmpegthumbnailer -i /Public/RO/Fotos/dns320l/IMG_20141018_053648.jpg -o po.jpg
You might try "ffmpegthumbnailer --help" for help
No, any generic computer, linux, Mac or MS-Wins will do the job.