A User-Agent is supplied by the client. Software can modify it, and browsers can reduce the detail they expose. Parsing a Chrome-like value does not prove the request came from an unmodified Chrome browser. The absence of a device model does not prove that the request came from a desktop.
Some browser details may be available through separate User-Agent Client Hints. Those headers and browser APIs are not included in a pasted User-Agent value. This parser does not collect them, verify a visitor's identity, check an IP address or assign an anonymity score.
Use the current environment checker when the task is to inspect the browser and network making the current visit. Use this parser when the task is to interpret an arbitrary value from a request, log or example.