I'm running 10.5.8 on a 2008 iMac and I'm fine. But now my Free Avast has expire

I’m running 10.5.8 on a 2008 iMac and my Free Avast has expired: what am I to do?

Advice please -thx!

You are posting in wrong forum section

Avast Mac Security >>> https://forum.avast.com/index.php?board=5.0

FAQ >>> https://support.avast.com/support/home