Recently I’ve been starting up quick web projects and a number of external services are recommend (Neon, Resend, Railway), and if I just let the agent rip, signed-up for and implemented. Is it confirmed any LLM producer or provider has been receiving kickbacks for these technical decisions?

Legally they would gave to disclose with the recommendation that its a paid advertisement. That said, they were also legally not supposed to scrape the entire internet for training so if they are getting kickbacks I wouldn't expect a confirmation.