Portrait Pro 18 & Landscape Pro 3 no longer work as plugins from Affinity Photo which used to work in 1.6.5. When either are used Affinity locks-up where it needs to be killed in Task manager. I know they are not supported plugins but as they are fairly popular I hope they are included as a supported plugins in the near future.
The only thing that has changed is that we now provide an ICC profile to the plugins, in order to ensure that images are correctly colour converted. None of the plugins mentioned are officially supported, so we'll have to speak to their developers to find out how they handle the ICC profile that we deliver, and see if we can reach a solution.