Plenty of manufacturers offer battery upgrade programmes, the one form Apple is even reasonably affordable these days. Plus there are third party upgraders that will do it for you for popular models. You do need to bear this requirement in mind when buying though.

Phone manufacturers should be forced to provide free battery replacement on all their phones. Otherwise they should make it a simple process for consumers to swap the battery out.

I still have a Samsung S5 phone with removable battery, had it for years. I don't know if there's phones on the market with replaceable batteries, I have not bothered looking for a new phone.