Under COBRA, you can keep the health insurance you already had through OT, but you pay the full price. When I left (in 2024) the full price was more than four times what was coming out of my paycheck while still there, but I don't know what the current pricing is like. If I recall correctly, you have 60 days to decide and if you sign up, it'll be retroactive. You don't have to decide today. The company is legally required to give you access.
If you have a spouse with health insurance, leaving your job should count as a qualifying event for getting added to your spouse's plan, which will very likely be less expensive. I don't know if it counts as a qualifying event for ACA. I don't know the timing requirements for either of those options.