The example isn’t meant to be a fully-fledged solution, just an example of how to launch the portal on demand.
You seem to have decided that the WiFiManager built-in solution isn’t elegant enough for you, and you don’t want to put the effort into getting the alternatives to work, so I’ll leave you to explore alternatives.
One thing I would say is that if you go down the route of the alternative that @khoih has suggested then this uses modified versions of the current BlynkSimpleEspxxxx.h library files. The originals of these files may be updated in future, and if the modified versions aren’t updated to keep track with them then you could find yourself in a dead-end in future. Also, those modifications may break something else that hasn’t been identified yet.
Either way, as they aren’t the core Blynk library files then you may find that you get less support from the community when you’re using them.
Here’s an example of a similar issue of using a modified version of the core Blynk library files that I came across recently…
Pete.