>>51753111I don’t have it all worked out, but the best starting place is to separate the Mega Evolution timeline from the timeline with no Megas.
The mega timeline starts with Let’s Go, making Elaine the hero who took down Team Rocket and would become Champion against Trace. That said, we learn from Pokémon Evolutions that Green (and likely Red and Blue) were still the original trainers sent out to complete the Pokédex. Green seems to be the only on focused on that goal. Blue is more political, organizing the fight against Rocket overall and later becoming a gym leader. Red is a mysterious Master Battler.
This fixes the timeline issues related to Sun and Moon. They are part of the mega timeline, so the Minna/Red age issue isn’t an issue.
Kalos and Hoenn events probably take place at similar times in the mega timeline, with Kalos being first because mega evolution is mostly studied there.
All the original games from Generation 1 to 5 take place in the non mega timeline.
Galar is likely non mega as well since no one mentions the possibility of mega evolution.
