No, not nextcloud, it's the photos on my website. They are CC-BY-NC-ND-4.0 licensed, which genAI doesn't respect in any form.

I added these in nginx.conf:

    map $http_user_agent $blocked_user_agent {
        default 0;
        "~*AI2Bot" 1;
        "~*AI2Bot-Dolma" 1;
        "~*Amazonbot" 1;
        "~*anthropic-ai" 1;
        "~*anthropic.com" 1;
        "~*Applebot" 1;
        "~*Applebot-Extended" 1;
        "~*AwarioBot" 1;
        "~*AwarioRssBot" 1;
        "~*AwarioSmartBot" 1;
        "~*Bytespider" 1;
        "~*CCBot" 1;
        "~*ChatGPT-User" 1;
        "~*ClaudeBot" 1;
        "~*Claude-Web" 1;
        "~*cohere-ai" 1;
        "~*cohere-training-data-crawler" 1;
        "~*DataForSeoBot" 1;
        "~*Diffbot" 1;
        "~*DuckAssistBot" 1;
        "~*FacebookBot" 1;
        "~*FriendlyCrawler" 1;
        "~*Googlebot-Extended" 1;
        "~*Google-CloudVertexBot" 1;
        "~*Google-Extended" 1;
        "~*GoogleOther" 1;
        "~*GoogleOther-Image" 1;
        "~*GoogleOther-Video" 1;
        "~*GPTBot" 1;
        "~*iaskspider/2.0" 1;
        "~*ICC-Crawler" 1;
        "~*ImagesiftBot" 1;
        "~*img2dataset" 1;
        "~*ISSCyberRiskCrawler" 1;
        "~*Kangaroo Bot" 1;
        "~*Meltwater" 1;
        "~*Meta-ExternalAgent" 1;
        "~*Meta-ExternalFetcher" 1;
        "~*OAI-SearchBot" 1;
        "~*Omgili" 1;
        "~*Omgilibot" 1;
        "~*openai.com" 1;
        "~*PanguBot" 1;
        "~*peer39_crawler" 1;
        "~*PerplexityBot" 1;
        "~*PetalBot" 1;
        "~*Scrapy" 1;
        "~*Seekr" 1;
        "~*SemrushBot" 1;
        "~*SemrushBot-OCOB" 1;
        "~*Sentibot" 1;
        "~*Sidetrade indexer bot" 1;
        "~*Timpibot" 1;
        "~*TurnitinBot" 1;
        "~*VelenPublicWebCrawler" 1;
        "~*webmeup-crawler.com" 1;
        "~*Webzio-Extended" 1;
        "~*YouBot" 1;
      }

and then in each site's config:

      location / { 
        if ($blocked_user_agent) {
            access_log /var/log/nginx/blockedbot.log ncsa;
            return 401;      
        }

But it's far from perfect. For better results, https://github.com/mitchellkrogza/nginx-ultimate-bad-bot-blo... is probably better, but it was a tad too much for my needs.