Atmega328p screen + midi, possible?
Of your three functions (DAC, screen and MIDI) only one (MIDI) actually uses UART.

The other two devices are SPI devices which, while it is a serial protocol isn't UART (serial is a concept not a protocol).

Connect the DAC and screen to the SPI port (you can share SCK, MOSI and MISO, but select different CS pins) and you have the UART pins (0/1) available for MIDI use - as long as you don't want to use the USB connection which is linked directly to those pins.