Shoot with smaller sensors and step down your lens. The bigger the sensor the shallower the depth of field at given f-stop. For example when shooting with an APS-C camera at f2.8 you're going to get the same amount of light on the sensor but less background blur than when shooting on a "full frame" camera at the same f-stop. So if stepping down the lens is not an option because there's not enough light you can still get a little bit less background separation and blur when shooting with APS-C or MFT cameras. Also the wider the lens the less background separation you get. 135mm lens at f2.8 is going to have razor thin depth of field while a wide angle 28mm is going to get way more in focus. Also hyperfocal distance. With wide angle lenses you can get pretty much everything from few meters away all the way to infinity in focus at the same time. That's why (I think) all phone lenses are wide angle.

Shoot at high f numbers - as high as the lens will take without inducing diffraction.

Shoot at f/64

Shoot at a higher fstop with a sensor with a high native ISO, like 12,800.

Focus stacking.

pinhole camera and an insane amount of light.

Or, multiple exposures and HDR.