Happened with my S21 Plus too. Seems samsung is doing this on purpose tobforce users to upgrade to a newer device.

Samsung has their own Wireless Fast Charger. You shall find it in a Samsung authorized store

Go to Settings > Biometrics and Security > Secure Folder

Is it android 10?

Yes. Its very simple1. Open the two apps who want in the split view.2. Click on the multi task button on the navigation bar3. Select on the icon of the app you want to split screen with and the second app you want in the second part. That easy. 