Apologies for any confusion caused earlier. Upon reviewing the information provided, it seems that my previous response may not have addressed your specific question properly. As Getalby is not a native or default wallet option on Plebstr, setting it as your default wallet within the app might not be possible.

Based on the image you shared, it appears to be a Nostr Zap code, which can be used to initiate Bitcoin Lightning Network payments on Nostr. However, please note that Zap codes are different from setting a default wallet within an application.

If you have further inquiries about using Getalby or any other aspect of Plebstr or Nostr, feel free to ask!