Using OKRs for a company organized as a monolith is like using a truck to pick up family groceries. It MIGHT get you there, but it will be slow, noisy, and unnecessarily painful.
What's a monolith?
Separate functional teams not organized as squads. One big engineering team rather than smaller mission-based teams with their own PMs, Designers, Data science etc.)
Re-think your culture and your org chart before putting lipstick on a pig.