Hello Mei Sing Wang,
There are two ways in which you can use MATLAB for developing programs to run on Raspberry Pi.
a) Install MATLAB on your Desktop (any OS among Win,Linux,Mac would work).
b) Later, install the MATLAB support package for Raspberry Pi. See below link,
a) Instead of installing MATLAB on desktop, you may use MATLAB Online. See below link.
b) With MATLAB Online, you can access MATLAB directly from your browser.
However, to use MATLAB for Raspberry Pi in MATLAB online, the procedure is different compared to a MATLAB Desktop installation. Please follow the below link for the instructions to support Raspberry Pi from MATLAB Online.
Coming to your orignial question on MATLAB suppport for Raspberry Pi Buster image, it is supported from MATLAB Ver R2020b on Desktop installation(Approach 1). MATLAB support for Buster image in online (Approach 2) is not supported as of today. However, it may be supported soon.
Please consider installing Raspberry Pi support package on MATLAB(R2020a ver) Desktop to work with Buster image for Raspberry Pi 3B+ or 4B.
Hope this helps!