You mention that your metricbeat upgrade was from 6.x to 7.x, which versions were these? If you were running a version of metricbeat older than 6.7, it was necessary to first upgrade to 6.7, and then to 7.0 due to breaking changes.
Here's the documentation for the above.. In particular:
We recommend that you fully upgrade Elasticsearch and Kibana to version 7.0 before upgrading Beats. If you’re on Beats 6.0 through 6.6, upgrade the Elastic Stack and Beats to version 6.7 before proceeding with the 7.0 upgrade.
Upgrading to 6.7 is required because the Elasticsearch index template was modified to be compatible with Elasticsearch 7.0 (the
_type setting changed from
This does sound like an index template problem due to, as you point out, the index names not containing the date.
However, if your upgrade process followed the guidelines, it would be helpful to know if your documents contain the correct fields for displaying the Infrastructure UI. The fields in question can be found here.