Framework not found FBLPromises (Swift Package Manager)
I've not checked to make sure I've not introduced other errors further down the line, but I think the problem was caused by Linker Flags being retained in the build settings.
I went to the Target -> Build Settings -> Linking and deleted everything under 'Other Linker Flags' (OTHER_LDFLAGS is how this is reflected in the project.pbxproj file according to my git diff).
File now compiles and runs successfully, if I find some subtle bugs later that might be caused by this I shall edit this answer accordingly!
Library not loaded: @rpath/FBLPromises.framework/FBLPromises iOS 13.3.1
You are probably using free developer account. Apple blocked utilizing external frameworks on free accounts with 13.3.1 upgrade. Try downgrading to 13.3 if still possible or buy Apple Developer License.
UPDATE 04/2020: Upgrading to iOS 13.4 and XCode 11.4 currently solves this issue.
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