The burial sequence in Elite: Legacy is very reminiscent of the description of Trinkets of Hidden Fortune and I do wonder if it was pointing us towards them and the now-abandoned TDW missions. If so, then I fear it is a redundant clue but worth bearing in mind, in case the Trinkets have been repurposed with a different role - after all, when TDW mission were removed, it would have been a good time to remove the Trinkets - but they did not.
This sounds approximately like ancestor worship found any many cultures. So, allow me to propose something:
Our ships look like they have a Guardian-inpired interface. Additionally, crystals are a common component of Guardian materials and the same is true of multiple engineering-related human ship-board components. Further, Trinkets of Hidden Fortune are described as follows:
Trinkets of Hidden Fortune
This container appears to hold an assorted collection of low-value trinkets, knick-knacks and statuettes. Such trinkets are generally used by superstitious pilots to try and win favour with Lady Fortuna. However, these particular knick-knacks have a much more valuable prize hidden within.
I think we need to take these to human crash sites (orbital and planet-side) and the Ancient Sites and Guardian sites and see if they react to occupied escape pods and Guardian Caskets.
Mark my words: this goes back to pretty much every independent permit system there is with a special emphasis on the following systems: Isinor, Van Maanan's Star, Sol, and very possibly Peregrina.
Isinor (very close to Ryder home system):
This pastoral system supports an agricultural economy but doesn't welcome strangers. So much so that the governing council won't permit a starport in orbit for trading. The permit for this system can be obtained via the Chapter of Isinor faction.
Van Maanan's Star:
This system was given to the Guardians of the Free Spirit religious sect by the Federation in 2480. They believe in maximum hardship and live underground on several of the inner planets of the system. It is forbidden by Federal Law to enter the system without the permission of the Guardians. The permit for this system can be obtained via the Sublime Order of van Maanen's Star faction.
The next part connects to the planet Undine in Peregrina (an Earth-like). This is the Guardian home system. I cannot explain what they are easily, so just read the link about the Undines. They are complex beings. This I believe explains a good deal of what we see in CMDRs and what we are told about our alien friends.
We are Guardians or at the very least some sort of hybrid (if you still haven't read the Undine link do so now - nothing will make sense without it). We aren't humans - at least not traditional ones. Almost all of Humanity was wiped out during WW3 or the incurable plague that followed (though the population has likely blossomed over the past 1,000 years - covered by Frontier gazetteer). This is why we can shapeshift our appearance in anyway we wish including apparent age, skin tone, sex, hair, etc). We merely look human. This is why only CMDRs can pilot ships. As you well know, normal humans have fared poorly when interfacing with Oresrian technology.
Somehow Trinkets of Hidden Fortune activates something of very considerable importance. Raxxla, perhaps?
P.S. Note: Maybe we really did make

with the Traditional branch. If so, this is promising and may means we can ultimately fix the relationship with both. For the record, it isn't necromancy if the "dead" are not, in fact, dead. It is learning from the wisdom of the elders.
en.wikipedia.org
en.wikipedia.org