I don't know the answer to your question, but FIRE is supposed to still be available for 2025 returns (2026 filing season), so FIRE can still be used for the next year.

I can't imagine that Intuit or any other company won't have things updated to IRIS by the time FIRE is discontinued.

https://www.irs.gov/e-file-providers/filing-information-returns-electronically-fire