What you can do to install 0.23 version is enable ATrpms.
Do the following from a terminal as root.
then copy and paste
name=Fedora Core $releasever - $basearch - ATrpms
Make sure you leave a blank line after the last line.
Save your work and exit.
Then type and enter
yum clean all
and you should see the atrpms repo listed, if so then on to the following.
yum install --disablerepo=rpmfusion-free-updates, livna, rpmfusion-nonfree-updates --enablerepo=atrpms mythtv-frontend-0.23*
Then see what happens, just keep in mind that mixing ATrpms with rpmfusion / livna is almost certain to lead to compatibility problems if you have ATrpms enabled all the time.
Post the output if you are not sure of the results, but, I think it should work for you.