I would definitely make use of a generic URL shortening service provided by Proton that could provide security features it already affords to other services such as: optional password or expiration by date and/or view count.

Similar request here: https://protonmail.uservoice.com/forums/932839-proton-drive/suggestions/50931542-easy-to-share-links-for-shared-folders-and-files where the shortening service would also apply to Proton Drive items (which looks to already be implemented for the most part).