The Boost for Reddit app still worked for a while after the big shutdown with workarounds, like creating a mod account or using revanced.
Not anymore, as of today, the Boost for Reddit app is completely 100% dead now.
Goodbye reddit forever, hello lemmy
See this discussion: https://www.reddit.com/r/help/comments/1d4d8bc/reddit_down_on_official_reddit_app_and_boost_not/?rdt=42748