I use my middle name as the username in all my accounts. But, recently, I realized that someone would probably know if the username "my-middle-name" belonged to me. The pattern is obvious. This becomes my concern due to the privacy (anonymity). Let's say, I give an opinion about a topic in the internet forum. My friends or my coworkers will know if that is me. So, now, I use a random username generator from Bitwarden [0] to generate a username. I use this approrach for new accounts since many organizations/websites don't allow to change the username.

I will probably use my middle name for certain accounts, like social media.

[0]: https://bitwarden.com/help/generator/#generate-a-username