A South Korean news outlet says that Samsung will reportedly make the Galaxy S21 series compatible with an S Pen. The report suggests that an S Pen-ready Galaxy S phone will help Galaxy Note users transition to Samsung's mainstream flagships. That is essential as the Galaxy Note 21 is billed to be the last of its kind.
https://www.notebookcheck.net/The-Galaxy-S21-series-will-support-S-Pen-inputs-as-Samsung-plans-on-merging-its-Galaxy-S-and-Galaxy-Note-series-of-smartphones-by-2022.496524.0.html