Have you tried the official instructions?
cd /tmp/
wget -O droidcam_latest.zip https://files.dev47apps.net/linux/droidcam_1.8.1.zip
sha1sum https://files.dev47apps.net/linux/droidcam_1.8.1.zip
# sha1sum: fb9f0737f45f1904c648dd0e6c1cfa7ff6089aa1
unzip droidcam_latest.zip -d droidcam
cd droidcam && sudo ./install-client
sudo ./install-video
sudo ./install-sound
sudo modprobe v4l2loopback_dc
If you want change the resolution mode, you can do it:
For DroidCam v4l2loopback-dc, you can change the webcam resolution as follows:
1. Close any programs using the droidcam webcam. Unload the driver:
sudo rmmod v4l2loopback_dc
2. Re-load it with new options (WIDTH and HEIGHT are numbers). :
sudo insmod /lib/modules/`uname -r`/kernel/drivers/media/video/v4l2loopback-dc.ko width=WIDTH height=HEIGHT
Standard sizes (Width x Height): 640×480, 960×720, 1280×720 (720p), 1920×1080 (1080p).
Note: MS Teams and Skype on Linux support only up to 1280×720 input.
3. Re-open the droidcam client and test it out.
4. Edit the text file /etc/modprobe.d/droidcam.conf with the new options to make the change permanent.