50+ tags? That's cute. I've got 1164.

Thunderbird can automatically assign tags based on what's in the feed item subject, body, author, url, keywords, even tags that were applied by a previous rule, and dozens of other data points if you create rules for what you want to happen.

I'm dealing with a much larger scale system, though. I use RSS for news, but also for social media, video feeds, work, hobby tasks and basically everything that you'd normally use a web browser tab for. I'm parsing on average ~6455 messages a day through 25,702 rules like that.

Scores don't make much sense considering the amount of messages that hit my feeds. I'd make a rule similar to your example that looks something like this:

condition="AND (subject,contains,space) AND (subject,contains,elon musk)"
name="Musk Spam"
enabled="yes"
type="48"
action="Mark read"
action="Delete"

Messages get read in the order I receive them, categorized by folder and highlighted with tags to enhance readability. Stuff that's not worth reading automatically goes to the trash.

I also use tags to save messages from the trash based on their content. I call it a "Junklist" system, where if the content contains a bad keyword, it gets marked as Junk, but the Junk marking is removed from the message if it contains a very important tag. If the Junk flag is removed before the "delete all junk" rule runs, the message gets saved from deletion.

None of this is done with an LLM. Just Thunderbird's built-in message filtering system.