For anyone still using Boost for Reddit, the latest revanced patch from wchill fixes the missing audio from redgif videos and adds the ability to restore some (not all) deleted content.
https://github.com/wchill/revanced-patches/releases/tag/v5.34.3
Posting here since r/boostforeddit is still set to inactive.
FYI: The repo is taken down due to DMCA. Not sure what can be done to patch now.