Insider trading requires breach of duty, if you don't have fiduciary duty with who you're trading against it's not insider trading. The required chain in the link is someone inside a contractual agreement providing information.

It's right in your own link, the filing-agent employee was convicted because he stole information he was contractually obligated to protect. Remove that obligation and there's no case. Truth Social owns the posts and is selling them with the source's blessing, nobody's stealing anything.

As much as I hate to say it, what they're doing with Truth social is very likely legal. The president does not have any contractual financial obligation to these companies, if he posts "everyone sell Intel, I'm going to regulate out of existence" to a group of people who paid him for this post early... there's no breach of contract anywhere.