Existing EFI Boot partition for Windows 10 not detected by Ubuntu 21.04 install!

[sandro.saccenti]

No EFI system partition was found.
But there is a /boot/efi partition for Windows 10

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: ubiquity 21.04.19
ProcVersionSignature: Ubuntu 5.11.0-16.17-generic 5.11.12
Uname: Linux 5.11.0-16-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu65
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.461
CurrentDesktop: ubuntu:GNOME
Date: Wed Jun 2 23:26:01 2021
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 21.04 "Hirsute Hippo" - Release amd64 (20210420)
ProcEnviron:
 LANGUAGE=en_US.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Steve Langasek (vorlon)]

unfortunately, I can see nothing in the logs attached which would explain this failure. To the contrary, the logs clearly show that partman correctly detects /dev/sda1 as an ESP. There are exceptions from ubiquity in the syslog, but they appear to be unrelated.