How can I update 11.10.6 El Capitan?

For the MacBook Air (11-inch, Early 2015), Monterey is the end of the line.

You can get Monterey using the appropriate link in this article. Before starting, I would recommend having at least one bootable clone backup of your current system, so you can recover in case something goes wrong.

How to download and install macOS - Apple Support

Here is Roblox's article on system requirements.

Roblox – Computer Hardware & Operating System Requirements

Back up your data, check the application compatibility table, click here, and then on the download link for a newer OS. That model's maximum one is Monterey.

Catalina and above won't run 32-bit software and split the functions of iTunes up; if you choose one of them, use Go64 as well.

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