Upgrader shows "Missing or invalid config.php"

[Fohdeesha]

Steps taken:

Switched to php 7.3 (also tried 7.2)
Uploaded latest release files (also tried alpha branch files) over current gallery2 install (old official install was latest official 2.3.2)

Navigating to the upgrade page, I get the following:

I verified the config is properly working (old install loads fine). I even checked the example config from your files and it matches. The config is attached (sensitive stuff edited out)
config.php.txt

[dakanji]

Hello,

I never quite completed this project.
Have you tried it as a new installation as opposed to upgrading?

[dakanji]

This is probably related to #77.