ubuntu lunar install (manual partitioning) never completes

Install of Ubuntu Lunar to
- hp dc7700 (c2d-e6320, 8gb amd/ati rv610/radeon hd2400 pro/xt)

The slideshow no longer has any moving bar... but still reports "Installing the system". No box has appeared for me to click as completed etc. If I look at the installer log however, it looks completed

Notes:

This install took some time, I cancelled the screensaver/black screen three times (a Lubuntu install usually only requires two) but that led me to click between SLIDESHOW & MESSAGE screens possibly a few times. (Lubuntu installer (calamares) also shows a % complete which makes me feel like progress is being made.. this not having %-indication made it subjectively feel 'slower' than it possibly was...) Window was showing messages which stopped moving, the messages sort of implying install had completed but the dialog window still reported

"Installing the system".

(I'll leave box in this state 60 mins before rebooting)

the last messages shown were
---
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: finish: cmd-install/stage-curthooks/builtin/cmd-curthooks: SUCCESS: curtin command curthooks
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: finish: cmd-install/stage-curthooks/builtin: SUCCESS: running 'curtin curthooks'
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: builtin took 293.859 seconds
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: stage_curthooks took 298.075 seconds
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: finish: cmd-install/stage-curthooks: SUCCESS: configuring installed system
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: curtin: Installation finished.
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: Skipping unmount: config disabled target unmounting
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: TIMED INSTALL_COMMAND: 298.081
Mar 07 17:46:47 ubuntu subiquity_log.3054[5114]: finish: cmd-install: SUCCESS: curtin command install
---

*** Expected Outcome

Dialog bog telling me install has completed & click okay to reboot etc.

** Actual Outcome

Window still reports "Installing the system" but moving-bar-graphic has disappeared & I wait...

ProblemType: Bug
DistroRelease: Ubuntu 23.04
Package: subiquity (unknown)
ProcVersionSignature: Ubuntu 6.1.0-16.16-generic 6.1.6
Uname: Linux 6.1.0-16-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.26.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.480
CurrentDesktop: ubuntu:GNOME
Date: Tue Mar 7 17:55:28 2023
LiveMediaBuild: Ubuntu 23.04 "Lunar Lobster" - Alpha amd64 (20230306)
ProcEnviron:
 LANG=C.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
SourcePackage: subiquity
Symptom: installer
UpgradeStatus: No upgrade log present (probably fresh install)