Probably not quite that old. Sexuality probably developed in the Proterozoic as a means of diversifying reproductive burden and offsetting parasites.

Multicellular life predates this by quite a bit.

So homosexuality likely dates back to the Proterozoic Era when the sexes where largely dimorphic and prone to shift as needed. Life … uh, finds a way.

Single cell life doesn’t have sexuality, not even all multicellular organisms do. And there are lifeforms like plants that throw around their pollen and hope that pollen of the opposite sex meet or make insects or alike distribute their pollen to other plants. That’s sexuality in the biological sense, too