Al-Ko have recommended various different lubricants over the years as the manufacturers have, and continue to, change(d) the names.
FWIW, I think Shell Retinax LX is probably still on the list, and the general listings on (replacement) compatibility names Shell Gadus V220 C2 (which is reasonably easily obtainable).
If you contact Al-Ko they will give you more generic advice (you may wish to do so for peace of mind), but the advice shown here should probably still apply:
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I've had a couple of Al-Ko chassised motorhomes, and have never been able to find/use the specified names. The most recent usage I've made is of Carlube LM2 (again, easy to source)..