We already know that the upcoming Samsung Galaxy S21 series will support the S Pen. Unlike the Note series, the S Pen included with the Galaxy S21 will be an add-on instead of a native feature. It won't slot into the phone like with the Note. And so, it requires a separate case for it. Samsung has prepared for that, at least according to these leaked accessories for the Galaxy S21 Ultra.
The S Pen will reportedly cost €40 (around CA$63), which is the same price as the stylus for the Note 20 model. Or it can be purchased as a bundle with select cases. The leak didn't specify how much the bundle will cost. But you might want to spring for one as the case will be instrumental for charging the stylus.
This issue isn't a problem for Note devices. But for the S Pen to retain its remote functionality, you'll need a way to charge it. The case looks a bit wider than usual to accommodate the stylus' thickness, and it holds the S Pen at the right position for the phone to charge it.
The S Pen seems similar to the model used for the Galaxy Tab S7/S7+ that used magnetic attachments for the tablet. But unlike the Galaxy Note's S Pen, it doesn't seem to have the click button-like top.
Source: GSMArena