MicrosoftExchangeFindFolderByDisplayName.cs

public static Folder FindFolderByDisplayName(ExchangeService service, string name)
{
    var folderView = new FolderView(100);

    folderView.PropertySet = new PropertySet(BasePropertySet.IdOnly);
    folderView.PropertySet.Add(FolderSchema.DisplayName);
    folderView.Traversal = FolderTraversal.Deep;

    FindFoldersResults findFolderResults = service.FindFolders(WellKnownFolderName.Root, folderView);

    return findFolderResults
        .Cast<Folder>()
        .FirstOrDefault(folder => folder.DisplayName == name);
}

Hey, thanks for this!
Three additions for anyone who comes after me:

1. Instead of filtering on the Server (and beeing limited to 100 folders), you can let EWS do the work for you by providing a search filter
2. In my case, I was allowed to omit the PropertySet
3. If you want to read out a specific mailbox of the ews-user, you can create a FolderId-Object containing that information

Result:

public static Folder FindFolderByDisplayName(ExchangeService service, string name)
{
    // 1. 
    SearchFilter searchFilter = new SearchFilter.IsEqualTo(FolderSchema.DisplayName, name);

    // 2.
    FolderView pagination = new FolderView(1)
    {
        Traversal = FolderTraversal.Deep
    };
    
    // 3.
    FolderId mailboxRootFolder = new FolderId(WellKnownFolderName.Root, "mailbox@example.com");

    FindFoldersResults results = service.FindFolders(mailboxRootFolder, searchFilter, pagination);

    return (results.TotalCount == 0)
        ? default(Folder)
        : results.Folders[0];
}

Thank you to both of you!