I have been operating a BitTorrent search engine for a few years (it is closed now), here is some advice if you want to launch it as a public website:

1. There is no absence of people opening the kind of torrent indexers, which you have in mind. In 2010s there were 5-10 such sites launched each year, even nowadays there are at least a few new indexers yearly. Almost all are closed within a year or two (at most). There are reasons for that, some are less obvious than others.

2. Most likely you will close your site after some time as well, here is why:

2.1. It will be difficult to find a hosting, which will tolerate it. Forget about Linode or Digital Ocean or any similar hosting providers - they will suspend your server (first) and account (later) after receiving a few automated DCMA emails. You can use some "second-tier" providers for some time, but eventually even they will get tired of you, you will be out the moment they receive the first paper letter from some law company, which represents some movie company or alike. You can use proxy servers or some other arrangement for some time, but eventually you will decide that it isn't worth the effort.

2.2. The same thing is true for domain provider. Yes, there are a few, which are more resilient, than others, but don't expect that they will protect you and your domain indefinitely for $15 per year. If your site is popular enough - the only option may remain to register a new domain every few months and hop between them. Eventually you will get tired of that. It may take half a year or a few years, but you will.

2.3. There are no money in torrenting nowadays. Forget about ads or donations - even thepiratebay cannot earn money that way, you will not be able to do that either.

2.4. Sadly, torrents are not that popular nowadays as they were 5-10-15 years ago. Some people still use them, but in most developed countries that's more like an exception, than the rule. The rule is netflix, spotify and alike. As a result, if you imagine large and happy community of users around your site - just don't, most likely there won't be any.

2.5. Don't expect just to launch a site and rest. You will spend at least 5-10-20 hours per week on its maintenance (fixing bugs, importing/cleaning data, adding new features, etc). It will feel fine at first, but more and more tiring as the months and years go by. Eventually you will get bored and stop any maintenance. Users don't like old/unmaintained sites, so they will be less and less interested in it. Eventually you will decide, that it isn't worth the effort to run it at all.

Don't underestimate possible legal problems. Tech people tend to simply throw them aside ("I will use a VPN/Cloudflare/Onion, no one will find me"), but here are my 5 cents:

1. Most likely - you site will not gain any significant popularity and you will decide to close it on your own. Meanwhile you will just be getting some automated DMCA emails/complaints from time to time, that's it.

2. Less likely - you site will be somewhat popular, it will become an attractive target for copyright owners and law firms (not as attractive as thepiratebay, but still). It usually takes just a month or two for some interested law enforcement agency to find out who you are (forget about all privacy protection methods you know, it is very easy to slip and eventually you will slip; you need to be lucky every time, they need to be lucky just once). Depending on what country you live, you will end up with a few thousand dollar fine (best case) or tens/hundreds of thousands + a small jail sentence + a criminal record. Not bad for a hobby torrent site with no income and a minimal community, is it?

Just to reiterate this one more time - it is VERY easy to find out who you are for any interested government agency [in your country], most of those 1-2 months will be spent waiting for replies for their letters and other similar bureaucracy, not for some CSI stuff.

Here is how it might go. First they will check the site domain and IP address and ask your hosting/domain providers to reveal you payment details (name/address on credit card). That's enough in 95% of all cases. Even if you use Cloudflare to hide your site IP and even if you use bitcoins to pay for everything - that will help only for some time, eventually Cloudflare will reveal your server IP and bitcoin transaction will be tracked back to your credit card. That's just a question of time and whether you are "wanted" enough or not.

If despite all this you still decide to go forward - don't forget to import all the available torrent data on the internet (there are tens of dumps here and there), that way you will have MUCH larger database, than just by DHT scraping alone. This is a good place to start: https://archive.org/details/torrent_metadata_archive_sample

Creators of such sites (including me) tend to focus too much on the number of torrents, no matter if they are active or dead. Regular users are interested mainly in active torrents.

Plus they want to see the current number of seeders/leechers, which is very difficult to keep up-to-date for a large database.

Plus they want to see a torrent creation/upload date, which you cannot get from DHT (you can record the day you found a torrent, but it will work only for newer torrents, not for historical ones).