I am pretty sure I have NEVER seen a filter after the oil flows thru the engine. this is because the oil returns to the sump by dripping off of every bearing and sliding metal surface..... In other words, there is no single "return circuit" to place a filter after the oil is dispersed throughout the engine.
EVERY engine design I have ever seen or worked on has the oil pump PUSHING the oil thru the filter then into the engine. This goes back to at least the 1960s.
It would be possible,
in theory, to put the filter between the pickup and the pump, and suck the oil through the filter, but that introduces a host of other problems with seals, and what happens if they fail.
But as you point out, having a filter before the sump simply cannot work with this type of oil delivery mechanism, which is nearly universal.
That's why installing a remote filter base is really very simple with most engines. All you need is an adapter to fit the existing filter base, the new remote filter base, and some oil resistant hose of a suitable size. Choose a filter that is at least equal to your existing filter in terms of area, flow, and pressure, and find a remote base to fit it.
Find some way to mount the new filter base, hook up some hoses, and you are done.