If you're looking to switch to graphene, you're limited to the google pixel line, which isn't a bad thing imo. Older models can be had for cheap, and they have good specs.

I'm on a pixel 6 right now and it's served me well. I'd recommend buying a 7 and up though, as the 6 is nearing the end of its support (I think graphene will support it for a few more years but I'd double check that before buying one). But a standard pixel 7 can be had for ~$150usd so not a bad call. The pixel 9 and 10 have AI chips in them so if that's a deal breaker for you, you're limited to the 7 and 8 (both still good options). And if you do move to graphene it kinda nullifies the whole AI chip thing anyway.

The default media player on pixels are kinda ass, however. They work fine, but the UI is janky. But there are plenty of media player apps available both on the playstore and through alternatives like f-droid. You can also find cracked versions of most "premium" apps pretty easily online. So if you find a media player you like, but it has ads or some other garbage, you should be able to find a cracked version with little hassle.

And completely unrelated to switching phones, if you're able to add a private DNS into your wifi settings like I can do on my pixel, you can add base.dns.mullvad.net to the private DNS box and it'll take care of 99% of ads (can't speak for youtube specifically) on your phone

I'm a huge nerd so take everything with a grain of salt how my experience translates to a non-techie.

Storing and playing music with Android is pretty straightforward. You just copy your music into the music folder. Then use either the media player your phone comes with or choose one of the 1 million other options on the playstore/f-droid. But i never liked Itunes to begin with. Not with the Ipod i had 20 years ago and not with the Ipad i had 10 years ago. It just gets in my(!) way of how i want to do things. If your whole music library and management revolves around itunes... uuh yeah, idk its going to be a new learning experience i guess.

Good quality camera shouldnt be an issue. Especially coming from a SE. Look up Samsung/Google/Apple camera blindtests on Youtube. The differences are minuscule and mostly about how they handle whitebalance (yellowish/blueish tint) and how pronounced the contrast in the shadows is. The UI of the camera will be different. But if you just point and shoot without needing more advanced settings it will be just fine.

If you want to use GrapheneOS or a custom ROM in general: Buy a Pixel and flash GrapheneOS. If your not a nerd other custom roms will be a huge pain to install. Graphene has a pretty straightforward web based installer which guides you through the process. The cheaper "A" models had pretty often issues with their batteries. But atleast Google just reimbursed everyone in those cases. I'm still on my Pixel 7 and i dont see any reason to upgrade until its support ends. Camera is still great, performance is still great, screen is great, battery life is okay. Choosing anything between 8-10 series Pixels should be just fine. Older ones have a shorter support period. Newer ones a slightly more expensive and a bit better. Pro models have a bit more ram and a telescopic camera for more zoom. Nice to have but i(!) wouldnt pay extra for that.

I have an iPhone SE too! Ublock Origin LTE is now on the app store so you can add it to Safari if you're software allows it.