If you are on Buster it definitely is time to update your system......I still run Buster, not sure if I can simply upgrade on that.
You can buy another SD card and install everything new. then you have your old sd card as a backup.
I have no idea how complex you have made your domoticz environment with all kind of scripts and plugins but by copying your old domoticz.db file into the new and up to date domoticz system you get everything working again. You probably have to install your python plugins with required python modules before you do that.