Migration of Blueprints has been relatively painless. Static Meshes required manual enabling of Nanite. Emissive Materials may require modification to prevent ‘Dimming in Daylight’. I demonstrate the problem here with solution in the description. C++ Plugins will require recompile and in some cases you have to update paths as some classes have changed.
LYRA Framework introduces completely new concepts for me with its abilities and definitions etc. A sad truth is, it made several of Marketplace Assets I acquired for UE4 to use as framework obsolete:( Many Materials i used in UE4 are low res in UE5 and look terrible 
I hope Publishers revisit and update resolutions for their packs.