I have been tinkering with Raspberries and trying to get blynk to work locally on them. After some time and a lot or trials and errors I managed to get it to work with self-generated SSL keys. The official guide works partially but generates an error when creating self-signed SSL keys. The followed steps were documented and can be found under the following link: https://github.com/warlock016/blynk-local-server
If you have any questions/remarks feel free to share them here! cheers and good luck!