DB train tickets without seat reservations will I be able to get an open seat?

Reservation is not required on trains in Germany. You can just board and look for a free seat. If there are no free seats you may have to stand till a seat becomes available. Most people that board that train in Munich will not be going to Prague, so a seat will free up maybe already after the first stop. Most people on that train will also not have bought tickets days in advance...

If you want to be sure of a seat get a reservation, You may get that at the station in Munich. All seats being reserved on a train does not usually happen in Germany. If you could not reserve a seat when booking it was due to that not (yet) being possible.

I was able to purchase train tickets from Munich to Prague but was unable to reserve seats. I am wondering if that means all seats on the train are reserved or is there some open seating available. Also does anyone know how early you can board the train.

For reservations, try it on the E-shop of Czech Rail (www.cd.cz). Select your train and click on "I want a reservation only". But don't worry if that doesn't work (some times it doesn't), the train will be full at most until Landshut or Regensburg, after that it is usually quite empty. Please note that it usually consists of two parts: one goes to Hof, the other to Prague. The cars to Prague are at the head of the train, which is an advantage for you, because many people are too lazy to walk that far. The cars to Prague are blue (operated by CD), plus one or two gray and white ones (by "Alex", the German cooperation partner of CD). If the train is on time, it is sitting in the station usually 15-20 min. before departure.

Thanks for all the useful info. Sounds like I may be able to find an empty seat hopefully.

I was in Germany for 30 days this year and only reserved seats once, and that was because I was going from Hamburg to Copenhagen, and it was highly recommended that I reserve them (and I'm glad I did). But for the rest of the trip, I did not reserve any seats on the IC or ICE trains and had no problem finding seats.

Just one more hint, even if it is no longer of any use to the OP: RegioJet has resumed its bus service from Munich to Prague, which was interrupted for two years because of the pandemic. There are initially two buses daily (9:30 and 16:30) in 4:30, one hour faster than the train.

Not all websites provide all options. I used the site that sla019 referenced to purchase a round trip ticket between Prague and Berlin four years ago. Everything was readily available (seat selection) on the Czech rail website but not apparent or accessible on the German rail website. In July the DB website was ripe with information and options.

I problem I have found is understanding the seat markings for when the seat is reserved. You may find a seat that is open now but reserved two stops later and then you have to find another open seat. The locals understand the system but I was always in the wrong seat.

how early you can board the train. It depends -- If the train starts at that station and it is just sitting there, often you can board 30, 45 minutes early. Otherwise you board when the train pulls in as it will only be there a few minutes before departing.

I don't see the train I have tickets for listed on either the db website or the Czech listed at all therefore I assume it is a full train. Will just have to wing it and hopefully we can get seats at some point.

Curious as to what site the OP bought the tickets from if the train isn't showing on the official sites.

I see the ticketed train listed on the db navigator just not listed as an option to buy tickets or reserve seats.

The trains from Munich to Prague are classified as local trains within Germany and therefore you can neither reserve a seat via DB nor can they sell out. In Czechia, they are classified as EX, the slowest type of long distance trains, and therefore you usually can book a seat at WWW.CD.CZ (I have no idea why that doesn't work now and then). Your ticket is NOT train specific. Which train do you want to travel with? (If at 10:43: that one is suspended all next week).

Thanks for all the advice found seats on the train easily enough. Lots of open seats but as we got closer to Prague the train filled up. My original train was canceled that must be why it wasn't showing up on the ticket sites.