As far as LKS German pattern flecktarn stuff is concerned, one will either use items with identical LKS pattern belts/shoulder harnesses or buy/make adaptors suitable for ALICE/MOLLE platforms for individual pouches. These adaptors can be bought or fairly easily made.
Those favoring German flectarn pattern items have some choices amongst later German and/or Chinese items which have MOLLE/PALS attachments. Latest batch of MOLLE/PALS mag pouches I bought were labeled "STURM-Made in China".
Not entirely thrilled with items being "Made in China". YMMV. I'd buy original German surplus, if it suits your needs, and if you can make it work for you. Chinese stuff; not at all so confident as to durability.
ETA: Second LKS-pattern Bundeswehr "Butt Pack" finally arrived from NZ. I'll play around with the whole set of items, including Canteen, Mag, and other pouches. German BW chest/shoulder harness has a platform on rear of shoulders/back which will allow attachment of some LKS pattern items, depending on their width. Surely a "Buttpack" can be attached there, and possibly a "Gas Mask" bag, which is somewhat larger in capacity, but has a plastic tab-over-pointed-plastic-stud which can be hard to secure.
This German BW rig, with Buttpack on rear shoulders and another below on belt, might be OK for limited duration. Sort of similar to M-1956 USGI rig, which was eventually discarded, although such M-1956 cotton canvas "upper back" attachment devices can still be found for fairly cheap. The M-1956 GI "upper back" attachment points on the shoulder harness/belt were made so that they interlocked with existing GI shoulder harness and the "Upper" butt pack could be doffed fairly quickly. While such GI items were eventually discontinued for various reasons, such auxiliary attachment devices might be useful to folks who are better trained in their usefulness than VietWar GIs, most of whom had scant training with their gear.
I think that sort of "versatility" is well worth considering. Suitable attachment points for such carriers on shoulder harness are easy and cheap to do. The "easily doff-able" harness for upper pack is also easy and cheap to make.
Back from sideways digression about USGI M-1956 gear!
Don't get me wrong, please. I'm NOT suggesting this sort of ancient German Bundeswehr gear to anyone. The German LKS attachment system has been, like many other nation's attachment systems, been supplanted to the far more useful, and universally used PALS system.
I'm pursuing this German Bundeswehr LKS-attachment thing mostly out of curiosity, and to see how such LKS attachments can be used with MOLLE/PALS gear instead of throwing away such decently made items. Waste Not; Want Not. If I can make either "sew able" adaptors, or "no-sew"
adaptors to allow adaptation of LKS German items onto ALICE/PALS platforms, I'll report back. Again, Waste Not, Want Not.
German Bundeswehr LKS pattern gear would NOT be my immediate selection of gear, but perhaps those having such items might find my observations useful, and thus be able to "Re-Purpose" such items along with more modern platforms.