I would just use a full wave bridge on your AC supply to rectify it. Then add a buck converter as a simple economical solution affording 5 V at 1 Amp and you should never need that much.DC DC 5V 1A
The link takes you to a board what bucks a high voltage to a low voltage. (1A max output) DC to DC
If the voltage drops from 30 to 5 then the current will increase 160mA in to 1000mA out.
I do not know how much current the computer board needs but less than 1A!. So the current from the 24Vac will be less than 160mA.
View attachment 122550