Yup, I was wrong about Shell. It's still there it seems. Just found UA: MEL 22 SECTOR DB-x D1-40 in USS that after scan showed Anomaly Detected Threat 4 . It took a lot longer since I stumbled upon the right signal source though (around 20 minutes or so). UA still points to Merope. Taking screenshots and recording it for reference.
Here are my results from checking the shell so far:
HIP 19175 - UA FOUND - 135ly from Merope
ARIES DARK REGION UE-P B6-1 - UA FOUND - 137ly
HYADES SECTOR BV-Y C17 - UA FOUND - 138ly
HYADES SECTOR IR-V B2-2 - UA FOUND - 140ly
HYADES SECTOR DL-Y D39 - NO UA FOUND - 140ly
HYADES SECTOR HW-W C1-8 - NO UA FOUND - 145ly
HYADES SECTOR EB-X C1-9 - UA FOUND - 146ly
HYADES SECTOR LX-T B3-0 - NO UA FOUND - 149ly
in the systems i found an UA, i found them pretty quick, mostly near the sun.
In the systems without UA, i searched a lot and relogged / revisited a couple times, but just found normal uss.
maybe someone else could check the non ua systems.
and thanks FD, the new bookmarks make things sooo much easier!!!
edit: just revisited the ARIES system again and found an UA.. so this all might still be just the new spawning mechanic..