Best suggestion I have is a bit involved. This is assuming the laptop uses an nvme storage drive, if not, replace "external nvme enclosure" with "external sata enclosure". Pull the windows drive out entirely, install a new drive. Install linux of choice on the new drive. Flip a coin, have a long conversation about expectations, or otherwise decide which to leave in the laptop before putting it back together. Tell BIOS to boot USB first always, then internal drive. If the external is not plugged in at boot, you boot whatever you left inside (windows or linux). If you plug in the enclosure, you boot the other. I don't know how windows will react when ran entirely from an external over usb (highly recommend a good enclosure that has good speeds and connects to usb c even better), but linux doesn't even seem to care.

My preference would be leave linux physically in the laptop, and keep the windows drive in the enclosure somewhere nearby for emergency use only. I'd bet you find that you go a long time without needing the windows drive (if ever), but if it is "too easy" to just boot to windows instead, most people will tend that way.