Connecting with a Cable
One cable is all it takes. There is less to set up than with Wi-Fi, it works with far more models, and it does not care about the brand.
What you need
A USB-C (OTG) cable, an Android phone and your camera. The camera end is either USB-C or micro USB depending on the model.
Charge-only cables have no data wires. They look identical, but nothing at all happens when you plug one in. Use the cable that came with the camera, or one that says it carries data.
Without a card the camera either refuses the connection outright or will not take shooting commands. Keep one inserted even if you only intend to receive photos on the phone.
Choose your camera maker
Other camera makers
There is no separate page for these, but they do connect over a cable. Here is what to change. Turning power saving off and keeping a memory card in applies to every brand.
If you would rather go wireless
Wireless takes different settings on each brand, but once it is set up you can shoot without a cable. There is a guide for each brand.