I must be still missing something since I see:
<dom-module id="state-card-uk_transport">
<template>
<style>
table {
width: 100%;
}
tr:nth-child(even) {
background-color: #dddddd;
}
td, th {
text-align: left;
}
</style>
<p>
<b>Next_train:</b> {{round(stateObj.state)}}
</p>
<table>
<thead>
<tr>
<th>origin_name</th>
<th>destination_name</th>
<th>scheduled</th>
<th>status</th>
<th>estimated</th>
<th>platform</th>
<th>operator_name</th>
</tr>
</thead>
<tbody>
<template is="dom-repeat" items="{{stateObj.attributes.next_trains}}">
<tr>
<td>{{item.origin_name}}</td>
<td>{{item.destination_name}}</td>
<td>{{item.scheduled}}</td>
<td>{{item.status}}</td>
<td>{{item.estimated}}</td>
<td>{{item.platform}}</td>
<td>{{item.operator_name}}</td>
<tr>
</template>
</tbody>
</table>
</template>
</dom-module>
<script>
Polymer({
is: 'state-card-uk_transport',
properties: {
hass: {
type: Object,
},
stateObj: {
type: Object,
},
},
});
</script>