Pixel 3/3a come to mind, though I'm not sure what they go for nowadays new, and they don't feature SD card expansion and also don't have the biggest batteries in the world.
Maybe an S9 or S10 could work too, as @kokakolia mentioned. I personally don't like the overaggressive post processing Samsung does with their photos though, but it might not be as bad as it used to be in the S5 days, as I haven't used a Samsung phone since then, so I can't say for certain.
Having owned both the S9+ and the Pixel 3a XL I can say they both have excellent cameras. Although idk what a used S9 would go for it might be a bit out of your price range.
Like @Mateyyy said, the Pixel 3a (or the xl) are options as well, I currently use a 3a XL as my daily phone. The Pixel 3a has the best low light pictures I have ever seen, and overall its a super easy to use camera for great pictures (and it does do 4k 30fps). I can't speak for the non-xl model, but the battery on mine will easily go a full day of heavy use. The main issue with the pixel for you is it does not use multiple lens so you can't get the benefits of an ultrawide lens or a lens with 2x zoom like the S9+ would have. The other issue is the Pixel 3a only has 64gb storage available with no option for expansion.
I really enjoyed my S9+, it had tons of great features (really fast slow-mo, low-light almost as good as the 3a, expandable storage, 2x zoom, etc.), but the phone was ludicrously expensive (I think I paid almost $900 for it). And mine had tons of issues. It completely failed after probably 8-10 months of ownership (the charging port completely died after about 5 months leaving me to only wireless charge until the phone started boot looping a couple months later). I really enjoyed the S9+ and wanted to love the phone, but I can never go back to a Samsung after spending so damn much on a phone that was a complete lemon, especially with their less than stellar warranty (it's only 1.5 years, and although I was fairly certain I owned the phone for less than that they wouldn't honor it).
The only other phone I could think of that might be good is the Moto Z family of phones. I've had a couple of their budget G phones and those phones are great values. I can't speak to the quality of the Z series in any way. But I do know they support their moto mods which always fascinated me. And they do offer a mod for the phone that's a add-on camera to the back of your phone that gives you 10x optical zoom, a real flash, and some other great features. The only issue again is price. I think the newest Moto z4 goes for around $500 USD, and the camera mod is another $199. And like I said I've never personally used one so I don't know what kind of photo experience they actually provide, I just know it's probably the closest a phone will ever get to a real camera.
