Lubuntu installer does not honor the 'flag', 'bios-grub' when GPT option is selected leading to failure to install grub.

I wanted to install Lubuntu (20.04) with btrfs root. I am using 20200208 media and during partition setup choose 'Manual' option and set partitions as follows:

/dev/sda1 8M unformatted (selected flag 'bios-grub', from the installer GUI)
/dev/sda2 2G swap
/dev/sda3 18G btrfs for /

Continuing with installation with this option, the grub-install fails complaining it could not see 'BIOS boot' partition. See attached sceenshot.

Solution is to manually set 'BIOS boot'. May be one could do it beforehand, which I did not try. What I did was to create partitions as above and while installation was in progress, opened up a terminal and manually set partition type to BIOS boot. I used parted and did 'set 1 bios_grub on'.

I checked on Kubuntu; if we choose 'Reservered BIOS boot area' option, the installer (ubiquity) remembers this and grub-install finishes successfully.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: calamares (not installed)
ProcVersionSignature: Ubuntu 5.4.0-14.17-generic 5.4.18
Uname: Linux 5.4.0-14-generic x86_64
ApportVersion: 2.20.11-0ubuntu16
Architecture: amd64
CurrentDesktop: LXQt
Date: Sat Feb 15 19:33:25 2020
InstallationDate: Installed on 2020-02-15 (0 days ago)
InstallationMedia: Lubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20200208)
SourcePackage: calamares
UpgradeStatus: No upgrade log present (probably fresh install)