Power solution Uno Wifi Rev 2 with 5 x motors, display

Hi,
i'm making a project using a Uno Wifi Rev 2 that controls 4 x 12v DC motors via 2 x L298N motor driver (powering peristaltic pumps), 1 x 12v Stepper motor via a L298N motor driver (powering a winch), and a 5v Nextion display.

I am struggling to come up with the most efficient way to power it all. The motors need 15v because of the voltage drop over the L298N, the L298N themselves need an additional 5v, and I am not sure which way to power the Uno (i've read powering it via the 5v pin is not reliable, so had currently been using 12v through the power jack). I have a 6A 15v power supply, but don't know if its a good idea to try to use that power everything.

Thanks for your help!

What are the motor’s current requirements? (DC and stepper)?