https://wccftech.com/galaxy-s21-plus-limited-8gb-ram-galaxy-s21-ultra-upgraded-to-16gb-ram/

Samsung is through with unveiling the Galaxy S21, Galaxy S21 Plus, and the more premium Galaxy S21 Ultra. However, it looks like the company took a step backward for the less expensive versions in terms of specifications. In short, there’s no way to upgrade the RAM on both the Galaxy S21 and Galaxy S21 Plus, as that option is only available on the Galaxy S21 Ultra.

According to the specifications listed on Samsung’s U.S.-based website, both the Galaxy S21 and Galaxy S21 Plus are limited to 8GB of LPDDR5 RAM. The RAM isn’t upgraded regardless if you go from the 128GB storage version to the 256GB one. Samsung may aim to keep the costs down and sell these two models at a competitive price by keeping the memory upgrade path locked.