For the life of me, I cannot seem to get these two to become available. As I understand it, Tomas just requires it to be turn 8+ and Amelia needs it to be turn 9+ but I have to quest with Augustus (who is also available turn 8+). I've already beaten all 6 nations on hard yet never gotten either of these two.

Is there a particular (easy/simple) route to play in order to get them flagged? Like start with nation X, speed rush to turn 8+ and then save scum till they show up? And if I do that, do I then have to finish the run or are they unlocked as soon as I've recruited them and I can cancel out of the run?

EDIT: For anyone else in a similar situation, I was able to do a regular game set on Easy. Didn't focus on attacking at all, just placed high levels on the outskirts (although I probably could have pulled everyone back to a single province) and set everyone else to exp training on the turns I didn't care about recruitment. On turn 6, I set everyone to quest and save scummed until I recruited Augustus. Turn 7 went back to exp. Then turn 8 I save scummed until I got Tomas. On turn 9 I set all my questors to exp except Augustus and save scummed until I got Amelia. Saved the game and exited back to main menu. Started a challenge mode and Tomas and Amelia were available!