Managed to assemble everything! But u-boot is still not playing nice:
U-Boot 2024.04-rc4 (Mar 15 2024 - 11:01:39 +0000)
DRAM: 1020 MiB (effective 4 GiB)
mbox: Header response code invalid
RPI 5 Model B (0xc04170)
Core: 20 devices, 10 uclasses, devicetree: board
MMC: mmc@fff000: 0, mmc@1100000: 1
Loading Environment from MMC... *** Warning - bad CRC, using default environment
In: serial,usbkbd
Out: serial,vidconsole
Err: serial,vidconsole
mbox: Header response code invalid
bcm2835: Could not query MAC address
Net: No ethernet found.
starting USB...
No working controllers found
Hit any key to stop autoboot: 0
U-Boot>
Does this ring a bell? @pyxlwuff @leon-anavi