I don't know if you are asking for how to actually develop the applications or how to build the business that includes an application but my go to for startup advice is Steve Blank (https://steveblank.com/). His stuff is easy to understand and helps me work through some of the difficult problems of creating a company from scratch.
Ask HN: What are your go-to blogs and books on building business applications?
21–22 of 22 posts
Re: Ask HN: What are your go-to blogs and books on building business applications?
#22Although it isn't a blog in the traditional sense - so forgive me if this doesn't hit your brief - the Software Engineering Daily Podcast (https://softwareengineeringdaily.com/category/podcast/) is a fantastic resource that offers an immense amount of information for a lot of different people, including those setting out to build business applications.
Each episode is accompanied by super detailed show-notes that summarize the episode nicely, so you can see if the episode has what you think you may be looking for.
Cheers and good luck.