Reinstall Ubuntu fails with an existing ESP

[Jean-Baptiste Lallement]

Groovy 20201020

= Test Case =
1. Install Ubuntu Desktop, reboot and verify that the target system has a biosgrub partition and an ESP
2. Install a second time
3. In the partitioning page, select "Reinstall Ubuntu"
4. Press on continue

= Expected result =
User can continue with installation

= Actual result =
A warning is displayed stating the no ESP has been found. If the user proceeds with installation anyway, it hangs when removing conflicting filesystem's files.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Thomas Szymczak (tszymczak)]

I am also affected on Ubuntu MATE.

[Thomas Szymczak (tszymczak)]

Here is the workaround I employed:
1. Open the Disks app to determine which partition is the EFI partition. It will be labeled "EFI System" under "Partition type."
1. Instead of selecting "reinstall" and getting an error, select "something else" to get manual partitioning.
2. Make sure the partition that previously had Ubuntu on it is used, will be mounted at /, and will not be formatted.
3. Select that partition, click the "Change..." button and set "Use as" to "EFI System Partition" in the dialog box that pops up.
4. Click "Install Now." There should not be any error about the EFI partition not being found.