Hello! My smartphone is dying, so I'll soon have to buy a new one. I'd like my new phone to have pure Android, without all the apps that manufactures install. Ideally I'd like to remove the majority of Google services too, but there are some that I can't replace yet, so I'm still dependent on, like google maps. What smartphone do you suggest me? In your opinion, would it be better to buy a smartphone with already stock android or to buy any smartphone, and then replace the OS?
If you want something devoid of Google stuff, you'll likely want to go with a phone that can be flashed with GrapheneOS, which can also optionally run Google Play services in a sandbox for more privacy and control.
If you want pure android, then a Pixel phone, but if you want to degoogle, no...
Else you can find very interesting powerful phone like PoCo F4 for instance and replace the ROM with the dozen ones available, check XDA.
Know that when you unlock bootloader/replace ROM, you will most likely lose the ability to pay with your phone, or play a cat and mouse game with magisk and addon and google Wallet.
If you want pure android, then a Pixel phone, but if you want to degoogle, no…
why? other than "your'e giving money to google just before removing google"
Know that when you unlock bootloader/replace ROM, you will most likely lose the ability to pay with your phone, or play a cat and mouse game with magisk and addon and google Wallet.
I didn't know about this, custom ROMs cannot run these kind of services?
Nope, Google Wallet does not run with unlocked bootloader or with root. There's a lot of programs made to avoid this but setup can be broken anytime with a Google update. If you absolutely want to pay with your phone, it can be nightmarish to install all kind of add-ons to bypass failing CTS.
I'd make a shortlist of phones based on price and hardware, then check the XDA forums to see which of the models on that list have good AOSP-based custom ROMs available. Generally, you'll have better luck with flagship models, but there are custom ROMs available for many, many smartphones - some even get updates for longer than the official firmware.
Another option is to use adb to uninstall bloat and crapware from the official images, which can be done with varying success depending on the phone's make and model. For example, I have a Samsung Galaxy A53 and was able to uninstall or disable most of the several useless or redundant apps it came with, but several I could not get rid of without breaking needed functionality (that shouldn't depend on them, but does for some obscure and probably illegal reason).
I agree with a few others here in mentioning /e/ from the Murena phone folks (you can buy a Murena phone with /e/OS preinstalled if you don't have an older device they've listed as compatible on their website).
If it's just about degoogling then you could look into phones with linux. There is at least Ubuntu Touch that supports a range of popular phones. I don't know about other distros.
Indian smartphone manufacturer 'Lava Mobiles' provides literally stock Android on their every latest phones. Also regular updates on phones regardless of price ! ❤️