I know for a fact that the S-Pens used in the Note 9 - 20 all have small capacitors for additional remote control and motion gesture functions. So those probably can't be used with the SGS21 Ultra. You would have to get a S-Pen from pre-Note 9 lines. If you want a S-Pen without those capacitors. That said even if you have a Note 9-20 S-Pen it will still function as a regular S-Pen.I'd say an older note phone s pen but if It aint charging not much use.
Well does anyone know if the s pen from older notes which use tiny batteries inside charge from the wireless charging from the rear of the phone?