SuperSpruce

Depends on your budget and location.

Unlimited budget: Sony Xperia 1 V ($1400). Has almost anything you'd want. SD8G2, MicroSD slot, etc.

High budget: Asus Zenfone 9 ($700). Great compact phone with a headphone jack. Alternatively wait for the Zenfone 10 to come out as it's coming out this week.

Or even the Xperia 5 V ($1000), a slightly downgraded version of the 1 V.

Lower budget: Sony Xperia 10 V ($450). Expensive for the specs but you get outstanding battery life, 25-50% more than any other phone on this list. And it's the only budget phone with a telephoto lens.

USA pick: Moto G Stylus 5G (2022). Can be picked up for $250 on Amazon and has excellent all-around specs for the price.

Europe/Asia picks: Xiaomi Redmi Note 12 Pro+ ($350) if you want good cameras for the price. However the chipset might struggle with MIUI from time to time.

Xiaomi Poco X5 pro ($300). Good all-arounder at this price.

Xiaomi Poco F5 ($400). Best chipset out of all of these budget phones, at nearly flagship levels.

Late to the thread but here's my thoughts:

Hardware:

1. Standard features like a 3.5mm jack and MicroSD slot.
2. Multiple USB ports (especially on tablets)
3. Thunderbolt port
4. Here's a simple idea: Instead of making a thin phone with a massive camera bump, you make a thick phone with the camera flush with the back, and use the extra space for a bigger battery?
5. User-replacable battery
6. Modules like the modo mods
7. Battery passthrough when charging
8. Upgradable RAM, internal storage???

Software (here lies my hopes and dreams that will never be manifested):

1. Starting off simple, a feature that lets you manually limit how much you charge your battery.
2. Manual over/underclocking controls for the CPU
3. Separate WiFi/data toggles
4. More control over how big or small icons and text is
5. Easy root access with app makers not getting all "you sus" over the fact that your device is rooted
6. No data harvesting (duh)
7. Better file management (and removing scoped storage)
8. Multiple logins to a phone (like what you can do with a desktop)
9. One app, multiple accounts
10. Just having the software take less system resources.
11. Open sourcing hardware drivers
12. Multiple floating windows like with a desktop OS
13. More than 3 split screen options
14. I'm sure there's a lot more I can't think of now

You now can't even sideload an app with a target SDK level that is too low. This locks you out of a bunch of older abandoned FOSS apps that often are very lightweight on storage.

But of course the restriction to sideloading older apps exists for all Android 14 phones...