Short answer: No — per the NFL, if Zxavian Harris goes to LSU for the 2026 season, he loses his draft eligibility for that year.
Here's the situation from his wiki page: Harris was released by the Saints in August 2026 and got a temporary restraining order to return to college at LSU (reuniting with Lane Kiffin). But the NFL immediately issued a memo clarifying that any player who returns to college for the 2026 season will be prohibited from signing with an NFL team that year and will lose draft eligibility. On top of that, the SEC and Big Ten enacted new pro-participation ineligibility rules that may block him from even playing college ball (from the Zxavian Harris page).
So it's a catch-22 — he'd need to successfully challenge both the NFL's memo and the SEC's eligibility rules to suit up for LSU, and even then he wouldn't be draft-eligible for the 2027 draft cycle either. His fantasy relevance remains on hold until the legal situation shakes out.