Here is a working patch for mesh_f2 in Blender 2.8.
Working without texture slot. Please See: line 51 to 61
following the discussion in F5856198:
regarding texture_slots / uv_textures removal: I think this needs a different fix though (otherwise the whole Adjust UV functionality of the addon is broken/obsolete...)
without looking in depth, I assume it is probably best to go with ob.data.uv_layers.active
(will doublecheck later...)
Sorry, didnt want to sound harsh btw and thx for the patch [well, not a patch, but.... you get what I mean...].
No problem, F2 and Bsurface are two of the most important and unique tools for retopo in Blender. And it should be included in 2.8 officially. Let me know if there are more fix please. Would be great for the entire community.