Paid torrent trackers don't really exist as far as I know, that's only really a thing on Usenet. The most common way to get into invite-only private trackers is through recruitment threads on other trackers, so if you aren't already a member of at least 1 private tracker it's hard to get into the scene to be honest. There are a few private trackers with open signups, or an ability to apply for an account and get manually approved, but those are pretty rare. The only one I'm currently aware of having open signups is pornolab, and as the name suggests that is a tracker dedicated to porn only. Another one that is very easy to get into is IPTorrents. It's invite-only, but they are giving so many invites to members that there are lots of people that will give you an invite if you just ask nicely
I have a script that I found somewhere and have made personal tweaks to: https://pastebin.com/RJf9kajk
Put it in a file called sub-clean.sh and check the instructions in the script on how to add it to bazarr
I have not noticed any issues with it, but there can of course be false positives (like someone saying the word "Facebook" in a series/movie), so your miles may wary. (this is why i leave the .trash.tmp file personally, so that i can restore the removed lines if needed)
and as always, this script is provided as is, but it might help someone out there