I just upgraded my Raspberry Pi3 and 3B+ to Buster from stretch. I had to re-do my whole Pi as the VNC wasn't working properly. I would strongly suggest a good backup of JMRI files, photo's and any files created by users. Also make note of any additional software acquired that's not in the original install eg., Julia. There were literally hundreds of files not updated from stretch to buster - in otherwords, a right mess!
