Train from Lyon to Chamonix

I'm sure people have. What's your question?

It's a surprisingly long journey by train BTW. Buses can be competitive, look at Flixbus or Blablacarbus, or even SNCF itself which runs buses as well as trains on that route.

The more efficient routing is to take the train from Lyon to downtown Geneva (or the airport),
and catch a bus from Geneva to Chamonix. The train from Geneva to Cham has at least one
(maybe 2) connections and slows down as it climbs up the Alps.

The train does stop at multiple stations in the valley, while the bus only stops at the Chamonix
Sud bus station in the town, so depending on where your accomodations might be, the train
might get you closer.

You do not have to pass through Geneve to go to Chamonix, not by train, not by bus. That is a detour.

What complicates the search for a good connection is that SNCF-connect.com is a website designed by people who hate humans. So it does not find all the convenient connections.

What you need to look for is trains to Saint-Gervais-Les-Bains. There are several direct trains per day. In Saint Gervais you will change to the train that climbs up to Chamonix. Total trip time a bit over 4 hours.

You can buy the ticket at the station in Lyon.