@patricksamphire I’m using Cloudflare with “bot fight mode” to block most of the ones that ignore the robots.txt. What you might try is the reverse, add the bots you want to index your site with the “Allow” directive, then at the bottom set a wildcard disallow.
I also have my sites geo locked to only the US and Canada as that is where my target audience is located, but Cloudflare will allow you to allow or block any country.