Most of the online resources related to medical device cybersecurity are from companies selling solutions.
Are there examples of high-quality independent blogs, resources for medical device professionals to refer to educate themselves?
Pretty much all of my experience in medical security to date has been playing games to paper over horribly insecure defaults that should never have been considered in the first place. Companies would rather things that are known to be insecure that others are using, so everyone is in the same boat, so to speak, than to choose something demonstrably more secure that nobody else is using.
In other words, learn about marketing, marketing forces, and securing things after the fact.
On the backend, use web API security best practices. This means only allow API access to authorized devices and/or users. Keep your database secure. There’s tons of resources out there about how to build a secure backend.
Cybersecurity isn’t nearly as complicated as marketers and would-be consultants paint it out to be. Granted, programs are complicated (firmware especially), so invest heavily in good testing to catch insecure code before they manifest into issues.
As far as the FDA is concerned, document everything, probably more that you think is necessary. Write up a clear set of requirements, verification and validation plans, and very thorough design documents. This benefits both them and any future team members that may need to work on the project.