Ideally, European LED tubes that come with starters are the proper direct retrofit LED tubes for preheat fixtures. Examples of such LED tubes designed for preheat fixtures include Osram SubstiTube CCG and UN lamps and Philips LEDTube EM and UN lamps:
Here is a video of an installation guide for Osram's SubstiTube tubes for preheat fixtures and eletronically ballasted fixtures:
https://www.youtube.com/watch?v=W0qM66RUbjYI am hoping to try some European LED tubes in North American preheat fixtures when I get the chance.