For years now, Collect has allowed users to select whether they want to use the dark or light theme from both in-app settings and by using the project QR codes. Like in a lot of apps, this was introduced before Android's native dark mode was introduced, and it was also introduced before multi-project support was added to Collect.
We've found in recent years that overriding the system theme (using a light theme when the system is in dark mode for example) can cause bugs - text will occasionally render white on a light background for instance. For many apps, these bugs are limited as the theme switch only happens when the app launches. For Collect however, this is exacerbated by the fact that different projects can have different theme settings.
Given that, the core team is planning to remove Collect's theme setting. This will mean that the app will always match the system's theme (the equivalent of using default "Use device theme" setting right now).
From our analytics, it looks like only 10% of devices are currently not using the default setting, and we expect these are mostly from older QR codes or projects. However, if you do have a use case that requires the app to use a different theme from the system, please let us know!