There is an environment variable, 'CONTENT_WARNING', which if set, changes quite a few things. For starters, it displays that content warning. But also:

• New accounts have 'show nsfw' ENABLED rather than disabled.
• When browsing anonymously, nsfw content is shown rather than hidden.
• When creating a new community the 'publicize on newcommunities@lemmy.world' checkbox is NOT ticked (that's new, sorry about earlier folks)
• NSFW communities are listed in the main communities list even when browsing it anonymously.

Also when making that I came up with this - https://piefed.social/post/1124924