I recently switched from Droidcam to Filmiic Pro (~$20), and it's pretty good. Filmic Pro supports clean HDMI out from the rear facing cameras on iPhones and s

I recently switched from Droidcam to Filmiic Pro (~$20), and it's pretty good. Filmic Pro supports clean HDMI out from the rear facing cameras on iPhones and some Android phones. You do need a capture card, but if you have a Camlink or the no-name $20 USB capture card that EposVox did a positive review on, you're good to go. On Android (I have a P20 Pro), I use a USB-C HDMI dongle meant for a Nintendo Switch, but it works with my phone plus it lets me charge the phone while using it. Filmic also has a "remote" app (~$3, iirc) so if you have an extra mobile device, you can control the camera app remotely (since the phone you're using as a camera has its screen is pointing away from you).