Yes, xvkbd isn't my favorite either.
I tried to build Onboard, which succeeded, but I'm getting
Traceback (most recent call last):
File "/usr/local/bin/onboard", line 32, in <module>
from Onboard.Exceptions import chain_handler
File "/usr/local/lib/python3.5/site-packages/Onboard/__init__.py", line 23, in <module>
from Onboard.utils import Translation
File "/usr/local/lib/python3.5/site-packages/Onboard/utils.py", line 38, in <module>
from gi.repository import GLib
ImportError: No module named 'gi'
The web says I'm missing python-gobject but that's installed.