The first???
I do not think so!

Anyone remembering the wetab tablet http://www.wetab.mobi/ Even the community forum is still existing.
You could install any linux distro .

It was heavy, huge and loud, because of the fan to lower temperatures of the Atom based system.

Also many of the early Stylus-based Siemens-Fujitsu tablet could run linux. I remember doctoring an LT C500 to run Debian. You had to extract the harddrive to install linux to the first, then install via a similar laptop and the linux kernel would pick the modules for the tablet hardware.