If you want a modular phone like that, you should buy the Fairphone 3, since it has a pogo pin connector for adding attachments. The upcoming PinePhone will also have a pogo pin connector for adding attachments, but its processor is so antiquated, that most types of upgrading aren’t really possible.
There is some possibility that Purism will follow the SHIFT5.X model where future models have parts that are backward compatible. See this post and this one for more info.