@Tony Thanks for reaching out. I have got the confirmation from my product group that unfortunately there are no plans to support .Net 6 and .Net core as of now in the Integration Account.
The feedback is already passed to the product team on supporting .Net core and .Net 6 and they may implement this in the future but no ETA as currently there is no plan.
I will suggest you to post this feature request here so other customers requesting the same feature can vote and the product team can review /prioritize the feedback/feature request.
The same is documented here in the prerequisites section on supporting only custom .NET code library. The same document also covers how you can Add referenced assemblies
While Logic App (Consumption) supports referencing external assemblies from maps, Logic App (Standard) currently doesn't support this capability. Referencing an assembly enables direct calls from XSLT maps to custom .NET code.