Looks like Season 6 of WHEN CALLS THE HEART is now available to watch on NETFLIX everywhere except the USA, Canada and the UK https://www.netflix.com/title/80036407. Aaron is in the episode titled A Call from the Past. Netflix lists this as episode 10. This episode originally aired in the USA (Hallmark Channel) and in Canada (Super Channel) on May 26, 2019.
EDIT: I’ve heard that it’s not available in Germany either. Only S1-S5.
[https://www.facebook.com/AaronDouglasFans/photos/a.366089811548/10157465729561549/?type=3&theater]
[https://twitter.com/AD_Fans/status/1223039291036594176]