The good news is the New Toast 19 I've just had an email about today is fully Catalina compatible.
Optimized for Catalina
Toast is fully compatible with macOS Catalina. Toast 19 supports macOS Catalina 10.15, Mojave 10.14, High Sierra 10.13, Sierra 10.12, El Capitan 10.11. (No mention of Big Sur)
The bad news is it will cost you $99.99 to upgrade. (£79.99 GBP)