Happy to help!
There are multiple ways, it depends on whether you enjoy technical stuff or not. :-)
Easy way is to use something like https://yesterdaysdomains.com
Slightly more advanced you can check out expireddomains.net
If you are somewhat technical you can get database dumps of all registered domains and write some code to watch for expiration dates and legit domain name drops (after safe periods).
@codeWhisperer
That's very cool. I think I've come across ExpiredDomains in the past.
Keep up the good work!