This was my first year doing duathalon’s. I used a combination of the high volume sprint plan and a 5k run plan on TP.
Phil Mosley has purpose built du plans on TP. I’ll be using one come January 2019. They do have some structured du plans (i.e. export to do on TR and your watch) not currently listed under the TP plans (I think they’re still under development, I inquired and was offered a 9-11 hour per week for 24 weeks). It’s for sprint and standard distance.
I just asked through his website… Looking forward to it.