I will have the warning later. It's Hugo, not ox-hugo
As you figured out, the RSSLink deprecation is from Hugo itself.. You probably found out the release notes where that was announced.
Regarding tagging ox-hugo, I don't think #Mastodon supports hyphens in tags, because the whole "ox-hugo" does not hyperlink when prefixed with "#".
Instead try #oxHugo next time (no hyphens but yes camelCase).
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