If I were selling a plugin I would explore a way to make it more like a SaaS that can expand beyond WordPress, leaving the plugin itself. Akismet is a classic example, and OptinMonster is a relatively recent one.
It's tough to pull off, but I think it's best from a business standpoint. However, depending on the functionality and "self-hosted" competition, it might be tough to sell.
For example, would anyone subscribe to a SaaS that lets you manage things like meta descriptions and title tags, when you can get all that functionality self-contained in a free plugin like The SEO Framework, where you don't have to worry about relying on a third-party service that could raise prices, shut down, etc.?