Well after much reading and testing I found the solution to outputting both opencover and cobertura in my Azure and local Tests.
It was a random read the showed the using of the runsettings.xml to control the coverlet output. This simple xml file
<?xml version="1.0" encoding="utf-8" ?>
<RunSettings>
<DataCollectionRunSettings>
<DataCollectors>
<DataCollector friendlyName="XPlat code coverage">
<Configuration>
<Format>opencover,cobertura</Format>
</Configuration>
</DataCollector>
</DataCollectors>
</DataCollectionRunSettings>
</RunSettings>
Allowed me to change my Test command to:
dotnet test --collect:“XPlat Code Coverage” --settings runsettings.xml
In the Azure Test task and it works locally as well.
This outputs both of these files:
coverage.cobertura.xml
coverage.opencover.xml