Summary
Users and user access on Linux based operating systems is a complex topic, mostly because of the incredible flexibility that Linux affords us. We can approach where users exist, how we create them, how they are managed, where our source of truth resides, and how those users can access their systems in so many ways. We have ancient technologies, we have extremely modern technologies. We can use nearly any mechanism, from any era, from any ecosystem and we can have many that we build ourselves and our unique to us. We can stick to well-known traditional processes, or we can easily build our own and work in a unique way.
There is no simple best practice for user management on Linux. Instead, our best practice is, like it so often is, that we need to understand the range of technological possibilities, how different risks and benefits will apply to our unique organization and know the products that exist on the market from open source to commercial, from software to services...