My mom needs a new phone. She is used to Samsung so Samsung it is. A54 is 400€ and S23 is about 800€. Is S23 that much better?
Samsung don’t have screen protectors like in OnePlus from factory. So installing them without dustor air bubbles is gonna be tough.
No comment on which phone to buy, but you should be able to have a screen protector installed (onstalled?!) by someone at a phone repair booth or similar. I’ve only ever put one on myself, and after the dust and air that got under it, never done it since. They do the job perfectly, no dust or bubbles!