Only the S21,S21 Plus and the Ultra are on the Android 13 schedule for November, the S21 FE is not mentioned. whilst eligible bound to be further down the line . https://www.sammobile.com/news/samsung-one-ui-5-0-update-release-schedule/
This article suggests it could be quite late but that is not definitive. https://www.getdroidtips.com/samsung-galaxy-s21-fe-5g-android-13-update/
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .