During installation error "An error occurred while configuring encrypted" causes data loss

[B D]

Briefly:
The ubuntu 20.04 installer writes things to disk before the "security prompt" is issued, and without notifying the user, causing massive data loss.

To reproduce:
- During installation select one volume as "physical volume for encryption" (One that already is a LUKS volume. For example one from an identical install made minutes earlier).
- press "back"
- advance, and select the same volume as physical volume for encryptiona gain
- A popup will appear (which did not appear the first time) "an error occurred while configuring encrypted volumes - the configuration has been aborted"
- Cancel installation
- Realize that changes were written to disk, and the original LUKS volume is now inacessible, and all data is lost, even though you never pressed "continue" and never agreed to write any changes to disk

I first posted this here, but it is clearly reproducible
https://askubuntu.com/questions/1304307/luks-encrypted-disk-gives-error-wrong-fs-type-bad-option-bad-superblock-on

[B D (clangor)]

This similar report also mentions changes being written to disk before accepting to do so
https://bugs.launchpad.net/ubuntu/+source/systemsettings/+bug/1761681

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

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