I don't understand why apps have gotten so hostile towards curious users.
For me, that's a hard Nope.
However I'm curious: do you apply this same criteria when trying software like Notion, Figma, or Google Docs? I assume you have different criteria based on whether the software is downloaded to your local device or not, but would love to understand why that's so.
Why add friction when it is obviously not necessary. Using the app without an email should be a primary workflow. Adding a temporary “try offline” mode is insufficient imo.
That being said if you have to require sign in Sign in with Apple is definitely the way to go.
Above you mentioned your preference for keeping data local to the device. That is one of the big motivators for even downloading the app. I don't use Notion or Figma, and prefer Pages or Numbers to Google Docs when possible, so yes I do apply the same criteria.
Even though I avoid it when possible, I can at least understand why a tool like Google Docs which is cloud first or collaborative by nature requires an account. Why a local-first app requires an email is a complete mystery to me. What's the benefit to me as a user? If you don't make that case, I assume it's for marketing and pass on it.
So now I avoid dropping my email when I can avoid it. Passing it out to try a new product just doesn't cross that bar.
Wholly local desktop or tablet apps have no business asking for my email because they have no credible need for it. Authentication is borne by other elements (the OS, my physical security, etc).
As soon as an email dialog pops up, it breaks my mental model of "local software" and I worry about what the software is doing under the hood. Especially if it doesn't come with any rationale about why it's asking me for it. e.g. Will I get more spam (and yes, the quarterly message you send me about product updates is spam in my book unless I explicitly asked for it - you're not as important as you think you are), does it phone home, what other telemetry is being siphoned off, etc? It's a red flag that smells wrong, and signals the software isn't behaving according to my expectations.
How would you feel if you walked up to a car that asked you to punch in your email address before you could open the door to take it for a test drive?
If an email is required and not optional, it's because the service/provider needs it for the service to work. If I'm using an online service providing my email is obviously for reasons that make my own experience better. If using an completely offline app, there is no clear way it makes my own experience better, so it must be entirely for THEIR benefit, which brings up what they're doing with that data. As a user when being introduced to a new product it's like meeting someone new and picking up on subtle social cues and deciding if they are trustworthy or not.
As a founder myself I know being able to identify users can benefit them. It's also irrational that signing up for an online service bypasses this gut check. However psychology is rarely rational.
Not to be brash but to you this is your dream and your vision but to me it's just an app and one I've no idea if I'm going to like. Stop making it hard to fall in love with your baby.