Water filtration when boondocking

No need to give up your backpacking techniques.
A different approach would be to use one of the many water purification products such as Aquamira
No filter to clean/replace and no chemical taste (that we have ever detected anyway). Lightweight and doesn't take hardly any space.
Disadvantage of course is that it doesn't remove solids.....or change the color (muddy water is still muddy water.....)
However, Alum does a "pretty good job" of settling out most solids if you are willing to give it time (overnight) to work.
With the combination of the two (Alum and Aquamira), I wouldn't hesitate to fill my tank from almost any water source (unless there was heavy metals or chemicals involved). The water may not look pretty, but it will be safe to drink.

Siphon/gravity will NOT provide enough pressure for any good water filter. Use a pitcher water filter.

You already have a way to filter/purify water as fast as you need to for cooking and drinking?
On trips where you expect to need more than what your tank holds use that and other water source from start. Fill glass or coffee pot from the water you have filtered, instead of faucet.
And for water that is "used"; How dirty is it? Your dish water is clean enough to carry the cornbacked snake out of camper, so is what you can catch in a bucket between your feet while you shower. If you catch the water as you rinse dishes, add soap and boiling water next time you do dishes, can save a lot of water.

We have had a Berkey for several years with 4 of the black filters. It isn't just a water filter but also a purifier, big difference! You won't need replacement filters for many years as you just occasionally scrub the filters clean, unlike most other short-lived systems. It is gravity filtered, but the water runs through fairly quickly.

We use it constantly for drinking and cooking at home and always take it camping with us. It sits on the counter and gets strapped in some cleats when traveling (water must be low otherwise it will slosh out on rough roads). It gets filled at the camper sink out of our FW tank. We have yet to use "pond" water, rain water, etc., but feel confident we could if we had to.

100% recommend this simple and effective system if you have a place to put it in the camper. Plus, if there is a zombie apocalypse, you know you can always have clean water. I think pricewise, it pays for itself quickly.

Are you planning on filling your water tank from streams, lakes, or other untreated sources?

I would avoid that if at all possible. In fact after years and years of RV travel and lots of boondocking, I have never had to do that.

Yah, I hear ya.

Probably overkill here, but,

One thought is the Berkey Systems, pricey but a good filter, just put on sink...
One time expense, worth it to me but I'm full time.. so..
I also have two filters on the hose fill up to tank, just to get rid of any debris..