Bayeux France to Interlaken Swit

If it's not possible to book one ticket all the way through, you may have to book a ticket from Bayeux to Paris and then separately from Paris to Lauterbrunnen (you would have to pass through Paris anyway so it's not as if this will be a detour). This will involve a station change in Paris, as trains to/from Bayeux go into Gare St-Lazare, while trains to/from Switzerland go from Gare de Lyon. This can be done via a 1-seat ride on the Metro (line 14 from St-Lazare to Gare de Lyon) or by taxi.

Here's a previous question on Paris to Lauterbrunnen: it looks like the normal path is to take a train from Paris (Gare de Lyon) to Basel, then switch to a local train to Lauterbrunnen.

"I am having difficulty finding a train from Bayeux to Lauterbrunnen" - where are you looking?

You can look this up on the DB website: https://www.bahn.com/en/view/index.shtml
Or on on: https://www.thetrainline.com/
Trainline (unlike DSB) will also sell you the tickets

I picked a date in mid-May, and got lots of options, including:

Bayeux dep 08:35, Paris St Lazare arr 10:49
Continue by Metro
Paris Gare de Lyon dep 12:23, Basel SBB arr 15:26
Basel SBB dep 15:59, Interlaken Ost arr 17:57
Interlaken Ost dep 18:05, Lauterbrunnen arr 18:25

Or you could split the purchase, either at Paris (as suggested above), or at the Swiss border. As this is a long trip, you may want to overnight in Paris.

Option B: Fly Paris to Zürich. Ypu then have to gte to Paris airport and from Zürich airport. This will be no quicker, a lot more changes and a lot less comfortable.

Another way from Paris to Switzerland is via Lausanne - we did that because cheaper trains to Basel were sold out at the time we wanted to book. Similarly easy to take SBB trains to Lauterbrennen (single ticket, transfer at Interlaken Ost)
As noted, this would be a looong trip. Just from Paris took most of a day.

First you need to take a train to Paris and than you can travel via Geneve, Lausanne or Basel.

See details of how to travel from Paris to Switzerland(it says London to Switzerland, just ignore the London - Paris leg):

https://www.seat61.com/Switzerland.htm

Andrew is right, but I also want to add that the Paris Gare de Lyon to Switz. (Geneva, Basel, or Zurich) must be booked in advance as it is a bullet train with reserved seats. You can do this via www.trainline.com
See also www.seat61.com

Once in Switz, you can buy a ticket from that town to Lauterbrunnen and that ticket will be good all day, so no worries if you miss a connection or want to stop for lunch. When you get off at Interlaken OST (not west) you will find the Lauterbrunnen/Grindelwald train on track 1 or 2 and you need to get in the properly labeled train car as the train splits along the way. Don't be afraid to ask; all the conductors speak English.

The Bayeux to Paris train is a couple of hours, as I recall. Allow at LEAST an hour to navigate thru Paris, the Gare de Lyon to Geneva is 3 hours, to Zurich 4 hours. Geneva to Lauterbrunnen is about 3.5 hrs, or Zurich to Laut is about 3 (and ask to be routed Zurich to Interlaken via Luzern for great scenery).