ubuntu risc v running on qemu

Get Qemu 
https://www.qemu.org/download/

Get ubuntu for risc v5 - I choose ubuntu-20.04.4-preinstalled-server-riscv64+unmatched.img
https://wiki.ubuntu.com/RISC-V
Uncompress with xz and give yourself some more space - I did this using a WSL 2 ubuntu shell as it was easier to use the tools from linux
xz -dk  ubuntu-20.04.4-preinstalled-server-riscv64+unmatched.img.xz
qemu-img resize -f raw ubuntu-20.04.4-preinstalled-server-riscv64+unmatched.img + 25G

Now you need some firmware and a kernel for risc V which can be downloaded from here
https://github.com/riscv-software-src/opensbi

Download the latest opensbi release and grab the files you need
cp opensbi-1.0-rv-bin/share/opensbi/lp64/generic/firmware/fw_jump.elf fw_jump.elf

Download a uboot deb so you can pull out uboot.elf
http://ftp.us.debian.org/debian/pool/main/u/u-boot/
 u-boot-qemu_2022.04+dfsg-2_all.deb - is what I choose
 expand it 
  ar -x u-boot-qemu_2022.04+dfsg-2_all.deb
  xz -dk data.tar.xz
  tar xvf data.tar
  cp usr/lib/u-boot/qemu-riscv64_smode/uboot.elf uboot.elf
  
  OK ready to roll
  
 qemu-system-riscv64 -machine virt  -m 4096 -smp 4 -bios fw_jump.elf -kernel uboot.elf -device virtio-net-device,netdev=eth0 -netdev user,id=eth0 -drive file=ubuntu-20.04.4-preinstalled-server-riscv64+unmatched.img,format=raw,if=virtio -cpu rv64
  
  username ubuntu
  password ubuntu

Looks like the FTP site does not maintain the RISC-V builds:

[ ] u-boot-tools_2022.04+dfsg-2+b1_amd64.deb 2022-05-14 20:13 202K
[ ] u-boot-tools_2022.04+dfsg-2+b1_arm64.deb 2022-05-14 20:13 190K
[ ] u-boot-tools_2022.04+dfsg-2+b1_armel.deb 2022-05-15 00:11 175K
[ ] u-boot-tools_2022.04+dfsg-2+b1_armhf.deb 2022-05-14 22:45 176K
[ ] u-boot-tools_2022.04+dfsg-2+b1_i386.deb 2022-05-14 22:44 206K
[ ] u-boot-tools_2022.04+dfsg-2+b1_mips64el.deb 2022-05-15 03:56 191K
[ ] u-boot-tools_2022.04+dfsg-2+b1_mipsel.deb 2022-05-15 06:02 195K
[ ] u-boot-tools_2022.04+dfsg-2+b1_ppc64el.deb 2022-05-14 21:29 218K
[ ] u-boot-tools_2022.04+dfsg-2+b1_s390x.deb 2022-05-15 04:26 189K

no RISC-V target.

has it percolated up to 'official' status?

https://packages.debian.org/sid/u-boot-qemu

Package: u-boot-qemu (2022.04+dfsg-2)

A boot loader for qemu
Das U-Boot is a cross-platform bootloader for embedded systems, used as the default boot loader by several board vendors. It is intended to be easy to port and to debug, and runs on many supported architectures, including PPC, ARM, MIPS, x86, m68k, NIOS, and Microblaze.

This package includes boot loaders for qemu/kvm.

Included platforms: qemu-ppce500 qemu-riscv64 qemu-riscv64_smode qemu-x86 qemu-x86_64 qemu_arm qemu_arm64

I found the above mentioned deb file here:
http://http.us.debian.org/debian/pool/main/u/u-boot/u-boot-qemu_2022.04+dfsg-2_all.deb

Theo, sorry for being so tardy getting back to you..., I will have a re run through the Gist and update with answers this week... Been very busy with one of my other projects at https://github.com/atsign-foundation