How can I connect a laser printer to my iPhone via bluetooth?

not unless brother has some app in app store which enables that, there is no generic Bluetooth printing system that is widely supported, and apples generic interface airprint is based on wifi not Bluetooth

you can read about airprint here About AirPrint - Apple Support

and you can read about the bluetooth printing profiles that do exist here List of Bluetooth profiles - Wikipedia

Hi,

The Brother HL-L2350DW is listed as supported in the About AirPrint article mentioned by Rudegar. This means that an additional app would not be needed if the printer and the iPhone are connected to the same network (Wi-Fi router).

Use AirPrint to print from your iPhone or iPad - Apple Support

Always make sure that the printer firmware has been updated to the latest version.

https://support.brother.com/g/b/producttop.aspx?c=us&lang=en&prod=hll2350dw_us_eu_as

Is there a special reason for not using AirPrint in this case?

Thank you for the information! Glad to hear that you found a suitable solution.

There is also a video "Set Up Your Brother Machine with Wi-Fi Direct" at https://www.brother-usa.com/support/hll2350dw .

Would it be correct to assume that you are using the Brother iPrint&Scan app in this very case?

As mentioned earlier, AirPrint does not require a special/additional app with iOS/iPadOS, nor additional printer drivers when used with a macOS computer. AirPrint supports wireless (Wi-Fi) or wired (Ethernet) network connections, normally via a Wi-Fi router. For some printers, the AirPrint technology may even work via USB. It may or may not work with Wi-Fi direct (where the printer provides the wireless network).

Using a Wi-Fi router (infrastructure mode) is the recommended method, especially when several devices/computers are involved, and when printing web pages et cetera is necessary.

Addendum

Regarding the router, an Internet connection is not needed for AirPrint to work. The interesting part is the local network (LAN, wireless or wired). This means that one could carry out a test with an old/spare Wi-Fi router as a (temporary) Wi-Fi hotspot for printing purposes only, if necessary. The WAN (Internet) port could be left open.

Thank you for the update about iPrint&Scan. Yes, if printing does not require an additional app, it indicates that the AirPrint technology can also be applied to Wi-Fi direct, at least for this printer model.