While for most long-distance walks I've gone over to the dark side for weight reasons (a D*** P&S), my lightest-weight & most compact walking film kit is a rangefinder.
Lenses are tiny (I carry 21 + 35 + 90 & sometimes a 15mm), also lighter (though the Leica M6 itself isn't as light as its size would indicate). The cheaper & lighter CV bodies could be a way to go.
AF, motorized advancement, long lenses & batteries are no-nos on long walks.
For landscapes & photographing the people you meet you won't need lots of automation & fast frame rates.
But you *will* feel every gramme you're carrying!