I think this regulation that comes into effect February of next year concerns all kinds of batteries, not only those of smartphones https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CEL... . I think, because I didn't doublecheck right now further than reading the first matching "appliances" paragraph (ctrl-f).

What I know off the top of my head, from reading the legislation a while ago. Is that technical reasons, such as waterproof devices, will still be able to retain non user replaceable batteries if it is needed to keep the device waterproof.