Simon 5 is coming soon!
Simon version 5 is currently in beta testing. It is a massive update, introducing a much-requested feature: syncing the Simon data between multiple Macs, plus a Simon Status service, a Link Checker filter, improved Find filter, iMessage and Speak Error notifiers, a new app icon, and much more.
Important: please note that Simon 5 requires a minimum of macOS 10.12 (Sierra), and will be a paid upgrade from Simon 4 after the beta. Purchasers since September 1, 2020 automatically get a version 5 license (that also works in previous versions).
Re: Monitor Blogs and Forums
Very easy. I'm not familiar with those forums in particular, but I monitor my own forums using Simon.
What you need to do is add a test for a forum page that lists new postings (e.g. the forum index), and add one or more filters to examine the relevant portion(s) of that page. For example, you could check the information about the topmost post, or a reply count, or similar values.
The Block filter is particularly useful for this, but a Find-based filter can also be useful.
I hope this helps.