In fact it improves search results, when you have multiple search engines turned on searxng does some sorting or filtering thing and manages to filter out lots SEO crap and ads from search.
montar
I2P makes anti-hacking server protections go mad. You first need to check whether your servers TOS doesn't say anything about port-scanning or hacking.
Sounds cool!
yt-dlp does a great job at ripping on majority of websites. If yt-dlp can't rip something then likely there is service-specific tool to do that i.e tidal-dl for Tidal (hi-fi music service). There's also a hardware method that involves cheap chineese hdmi splitters (it needs to be a cheap one, b/c they lack support for DRM) and hdmi capture card. Sometimes it's DVD or blu-ray ripping.
Ppl do it with UV LEDs and they claim it works. I never tested it, i'm dried-a-cactus kind of guy.
First thing that comes to mind is ye olde cheap opamp and a potentiometer. This aritcle claims hysteresis can be done with a resistor. Opamp output is not meant for relay, but it can control a transistor which in turn can control your relay just fine.
Edit: i've just re-read your post, there's no need for relays if you have low voltage, just get a transistor rated for more than 5V and make sure it wom't overheat.
Cloud and "serverless" solutions
for chat there's IRC or bit more modern XMPP.
It's more likely to be a sb like me who just gathers stuff like that for future use in (maybe) questionable way.
torrents have trackers, special servers that keep track of who's got which parts of a file.