Build failures on first install

[flim]

Pi Model or other hardware: Pi 4B
Power Supply used: 65W Xiaomi
RetroPie Version Used: v4.8.9 (e553dee)
Built From: Git clone taken today
USB Devices connected: Keyboard & mouse
Controller used: n/a
Error messages received: Could not successfully build x (detail below) x_libretro.so not found
Verbose log (if relevant): Can provide, but only shows file not found error
Guide used: https://retropie.org.uk/docs/Manual-Installation/
File: Multiple (detail below)
Emulator: Multiple (detail below)
Attachment of config files: Likely not relevant yet, but will add if required.
How to replicate the problem: Execute retropie-setup.sh and choose Basic Install.

Hi, this is my first post and first time trying to do anything vaguely clever with my Pi, so please be gentle!

After running the basic install and waiting for it to download/compile/install the various dependencies, the installer produced two error messages, one each for MAME and Mupen64Plus. See below.

MAME:

Could not successfully build lr-mame2003 - Arcade emu - MAME 0.78 port for libretro
(/home/flim/RetroPie-Setup/tmp/build/lr-mame2003/mame2003_libretro.so not found).

Mupen64Plus:

Could not successfully build lr-mupen64plus-next - N64 emulator - Mupen64Plus + GLideN64 for libretro (next version)
(/home/flim/RetroPie-Setup/tmp/build/lr-mupen64plus-next/mupen64plus_next_libretro.so not found).

I have confirmed that the locations specified do not contain the file referenced, but that's about the extent of my troubleshooting thus far. I tried a google search, but didn't find much of use, hence asking here.

The OS is Ubuntu, which I don't know if it's supported, but everything else seems to have worked up to this point.

Thanks in advance for any help/guidance you can provide and apologies if I've left out any critical info.