Using two Macs, one with macOS 10.12, the other with macOS 10.14.
Both have LO 6.2.4 installed, where the dialogues are in English.
Both had LODev 6.3.0 alpha1 installed, dialogues in English.
I installed LODev 6.3.0 beta1 over LODev 6.3.0 alpha1.
On one machine the dialogue is in a Spanish-looking typeface.
On the other machine the dialogue is in a German-looking typeface.
«Preferences->Language Settings->Languages» are set to English.
I then installed LODev alpha1 over LODev beta1 and the problem is now present.
I then deleted LODev plus the LODev folder in «~/Library/Application Support» and installed LODev 6.3.0 alpha1.
The language abnormality persisted.
I repeated the delete of LODev with the LODev folder in «Application Support» and installed LODev 6.3.0 beta1.
The language abnormality persisted.
Meanwhile, the Print dialogue remained normal in other applications.
There must be some other LO-related directory not in the Application Support LODev folder that needs to be deleted.