Does Duplicacy support hard links? If it does, how are they handled during backup and during restore (are they restored as hard links?)
I don’t think there is any special support for hardlinks. Backup will read two different files which will be deduped, and restore will restore two different files, so hardllinking will be lost. Generally speaking, 
operates on file content and does not preserve metadata such as file attributes. You may need to package your files into something like tar or fsarchive even if you want to preserve metadata.
That’s a pity as it makes Duplicacy unsuitable for my use case. Thanks for clarifying.