[PersonalOps]

Yes and no. Buffer and Hootsuite are 2 players in this game, both allowing to publish or schedule posts based on updates to an RSS feed you configure. Most blogging engines (WordPress, Jekyll, Hugo) come with RSS feed publishing by default.

The tricky part here is the quality of the posts will be bad. Each social network has its own social mores and taboos. Some examples:

Fediverse you refer to Twitter as "birdsite". Anything automated here, unless explicitly called out as a bot account, tends to get ignored as low quality.

Facebook does posts in long-form.

Twitter can thread it to be long-form, but each tweet needs to stand on its own with contributing to the overall narrative. Basic pagination type of splitting sticks out.

LinkedIn... I don't know anyone who posts there that isn't trying to artificially puff themselves up in corporate culture, promote their product/service, or some combination. I'm truly unsure what a "quality" post on there looks like, so go wild.

Basically, posting "<post-title> (<link>)" is probably the most ubiquitous, low effort ways of cross-posting your content but... it's pretty universally understood that it's low quality content and not likely to accomplish the originally intended syndication.