In your own giveaway you can promote whatever you want.

Yes. As long as you don't try to promote something that is listed in The below is a list of content that is not allowed in our community. Content consists of any material you post or make available through our site, such as discussions, links, comments, usernames, or Steam avatars. section of the guidelines it's fine.

So you can promote your friend twitch or your curator in the giveaway description. But for example not key shop or referral links.