The "rss" command:

Usage: fossil rss ?OPTIONS?

The CLI variant of the /timeline.rss page, this produces an RSS
feed of the timeline to stdout. Options:

-type|y FLAG
   may be: all (default), ci (show check-ins only), t (show tickets only),
   w (show wiki only).

-limit|n LIMIT
  The maximum number of items to show.

-tkt UUID
   Filters for only those events for the specified ticket.

-tag TAG
   filters for a tag

-wiki NAME
  Filters on a specific wiki page.

Only one of -tkt, -tag, or -wiki may be used.

-name FILENAME
  filters for a specific file. This may be combined with one of the other
  filters (useful for looking at a specific branch).

-url STRING
  Sets the RSS feed's root URL to the given string. The default is
"URL-PLACEHOLDER" (without quotes).