as a grapheneOS user, I obviously care about my privacy, hence why the iPhone will not be my main driver, the grapheneOS device will continue to be.

but I might be getting a free iPhone soon and I have an idea of what I would use it for (Podcasts as Apple Podcast is the best cross-platform podcast app I have come across) but am not sure what else I would be comfortable using it for as I don't know what actions are safe without having Apple gather that much data or telemetry on me.

I know that I won't be using iCloud on it. I have no need for Apple's data storage. Nor do I see myself ever using the App Store, except for installing a VPN app. I might install Signal on it but not anytime soon (not least of which cause Signal does not yet support multiple smartphone usages for the same device). I definitely won't use iMessage as I don't believe in using a messaging service that is limited to a specific ecosystem.

I will note that I wont install a SIM on it. It will be using Wi-Fi for the foreseeable future.

Given these things, i am not sure if there is anything i should be on the look-out for in terms of privacy concerns with the usages I have outlined above

Edit:

Based on the answers to my post, I am getting the sense I didn't explain my current situation, which fair enough.

I have audio and video podcasts I consume, for my audio podcasts that I tend to listen to while commuting and exercising, AntennaPod proved a God send for this, to the extent that I wanted to support the app financially until I saw that they said their costs are already covered and it made me appreciate them even more for their honesty.

However, I have a free iPad I got by accident (not worth going into here) and I prefer to consume my video podcasts on a bigger screen than my google pixel. I don't trust Google with tablet development after a bad experience with another tablet I had from them so that was out. so I decided to just use the free iPad and was delighted to find their Podcasts app also supports videos.

However, I wanted 1 service that I can use on a phone and tablet. AntennaPod does not have any iPad apps. I saw this page and the 2 alternatives seemed to be Pocket Casts and Podverse. I tried Podverse but the iPad app would not even launch for me, it crashed every time so I said goodbye to that.

reading into pocket casts, it seems they do collect some data and they do have the option opt-out of that but that could very well change, which means I'd be in a situation where I could be paying for a product while also having my data collected and I disagree with that business model.

So, Apple Podcasts is probably collecting some data on me but I figured all it knows is what podcasts I listen to, which isn't terribly useful (I hope) considering I have subscribed to podcasts from a feed I generate myself.

And I happened to already have an old iPhone lying around at home so I decided to switch to using that for my audio Podcasts and use my iPad for video podcasts and its sometimes glitchy since I would call the Apple Podcasts synchronization experience (between devices) half-baked at most but I can make it work for my use case. So I am already using a separate iPhone just for podcasts and I might be in the position where I get a new iPhone which would replace the current iPhone but not sure what new threats to be aware of privacy-wise. I would be upgrading from an iPhone SE first gen to whatever new version I am getting.