I wouldn't say the Fairphone 5 wins prizes for looks or functionality but it does show that it is entirely possible to make a phone with a replaceable battery and repairable components in a modern form factor. If they, a small boutique phone maker can do it, then there is absolutely no excuse that Apple, Samsung, Oppo etc. cannot do the same.
One failing of Fairphone is you cannot buy the mainboard (the core component) from their store. All the other components yes, but not the mainboard. The core is not just the CPU, flash but also some other things like microphone are on it. It would also be nice if people could order all the parts that make up a Fairphone 5 and assemble one entirely from scratch.
I've also read through their ethics / green reports in the past, and while it talks it up with "supply chain engagement" reports and so on, most of their components are still made to order by Chinese OEMs so how far does it go down the chain in reality.
I think this will be Apple's plan when the EU forces them to sell devices with replaceable batteries. The EU says end users should be able to replace the battery without special tools, heat, solvents. It doesn't say the battery can't be DRM'd up the ass, or how long or what quantity of replacement stock should be made available.
So I expect Apple will do exactly that - DRM'd expensive batteries in limited supply. So even if you wanted to replace the battery you won't be able to get hold of one. Maybe they'll allow OEM batteries but in the typical Apple way - gimping the phone and putting scary warnings on the screen that the battery is not Apple certified, that rapid charge, screen brightness, or something else is disabled. Because Apple are dicks.