Always learn as much as you can: I spend most of my time learning. Comp Sci is a science that evolves continuously, if you're standing still you're moving backwards. Set aside allocated learning time and stick to it.

Build and/or contribute: You already mentioned you'd made some contributions to open-source Bitcoin/Lightning services. This is awesome! Although job descriptions often have "3+ years of X" included in them, the team is trying to de-risk their inevitable hiring gamble. What they really want is someone who can build the things they want, you can demonstrate that without the years. (especially if you're sticking to that learning time).

Understand the bigger objectives: This one might not be too relevant here, but it's important to understand your role as a software engineer in a business. Your job is to identify and resolve business problems to increase productivity and profitability— not to write code. Always try to keep in mind the bigger objectives and do your best to facilitate them, using code as a useful tool to help you do so.