I use a micro four-thirds camera from Olympus. I bought it for two reasons, portability and being weather sealed. It's compact and with a 24-80mm type lens, weight and bulk is a non-factor. With a 17mm prime, I'll almost forget I'm packing it around.
https://www.peakdesign.com/products/capture/This capture clip from Peak Design was a game changer for me. You can screw it on to the shoulder strap of your ruck sack and clip the camera to it and it stays put. It has eliminated the need for me to carry a separate small shoulder bag. I can keep my cleaning kit/filters in my ruck. I can deploy the camera almost as fast as drawing a pistol from a holster. It will attach to a belt,also, if you don't carry a backpack.
I wouldn't want to pack a great big full frame camera this way, but the little m 4/3 is the camera I always have with me. That system is worth checking out if you value great portability and solid weather proofing. The image quality is great, as well.