I have the same issue on Samsung S23 Ultra/Android 14. The folder on the S23 is created as a subfolder inside /storage/emulated/0/ as Send/receive by the initial sync from another Android Device (Samsung Tab S6/Android 12). After the first sync the folder on the S23 is suddenly changed to Send Only and tells me that my Android version only grants Syncthing readonly access. On the TabS6 side it works fine.
Edit: I just noticed that the webgui on android still shows Send/Receive and it seems to work fine.