There is no specific reference/link to list known issues as per the release. Instead, we have resolved issues for every release.
Before every upgrade, Carefully going through the release notes for each patch/major release is one of the ways to be aware of new fixes & features. Few notes may include settings to enable/disable certain features in the platform.
We also recommend going through Pega 8.x upgrade guide to be aware of prerequisite configurations for the smooth functioning of certain OOTB 8.x features.
- Potential issues could occur from the upgrade (From 7.3.1)
For this, you need to perform the pre-upgrade assessment by knowing the latest changes in 8.3.1 which may impact your current application customizations. I remember we had a pre-upgrade estimator tool for 7.x, but the estimator for the 8.X versions is not available, and we suggest reaching to consulting team of Pega in your project to help with pre-upgrade assessments.