Omio is such a great app, for some reason many people on this forum don't like it at all.
"for SOME reason"? How about this reason?
A few years ago, my partner and I went by train from Lindau, Germany, to Rothenburg odT. The trip by train took just under 5 hours and we were able to do it with a 2 person Bayern-Ticket which costs 34€ (less than $40) today.
I went to Omio.com/app and searched for a trip from Lindau to Rothenburg. It recommended we fly from Zürich, Switzerland to Nuremberg, Germany on Lufthansa, 3h10 with a 1h20 change at FRA, for over $1500, with no explanation of how we were supposed to get from Lindau to Zürich or from Nuremberg to Rothenburg or the total time or cost.
So I clicked on train, and it told me are were no train connections for the trip I wanted to take. ??? That trip, by train, is still shown on the Bahn website. That seems like some reason to me.
At least Trainline got the train connection right, but it wanted over $56, 42% more than what the Bahn wants, which was less than $40.
That's why I always tell people that the Bahn website is THE place to go for German rail tickets.
Update: OK, I finally found the problem. Although I specifically typed "Lindau, Germany", the Omio website changed the search to "Lindau, Switzerland". I finally somehow forced it to search for Lindau, Germany, and then it did give me the correct train routing, but it still quoted the price of a 2 person ticket at $56+, not the $40- that the Bahn charges.
So, not only does Omio charge more than the Bahn does for the same ticket, but you can't claim that Omio is easier to use because it decided on it's own to change my search criteria, from Germany to Switzerland. And, even if I had wanted Lindau, Switzerland, it didn't show me Lindau to Zürich or Nuremberg to Rothenburg. Omio is worthless.
Apparently, to get the right starting point from Omio, you have to specify "Lindau (Bodensee), Germany".