I purchased a ZVS Tesla coil driver board and would like to convert the circuit to accept 230v AC mains input. Can anyone advise on the best possible solution to achieve this?

Link to board: [ https://www.aliexpress.com/item/ZVS...-Voltage-Power-Supply-DC-12V/32717751259.html ]

 

A 240V to 24V power supply is the way to go. That is how it is designed. There are many on Ebay and stores like that.
You must not feed that board with 240V directly. Running something like that directly on 240V sounds really dangerous. Besides that, the 240V is very low frequency and the Tesla coil runs at a much higher frequency.
Whatever you do, be very careful as it is a leathal device you are playing with.

 

Would it be possible to use a 20v AC directly on the circuit without modifications?

 

Would it be possible to use a 20v AC directly on the circuit without modifications?

No, I don't think so. But you may get away with running 20VAC into a large bridge rectifier and maybe not need a filter capacitor but so it will be unfiltered 28VDC unregulated.