I think some LH and LX flights to MRU are operated by eurowings and edelweiss. Be sure to double check the PQM and redeemable miles earnings, which may depend on the ticketing carrier, fare class, etc in different ways than for most LH and LX flights. (If it's LH cityline then I think it's the same as for regular LH flights...at least it has been for me in the past).
Eurowings:
https://www.united.com/cms/en-us/mar...spx?itemid=668
Edelweiss:
https://www.united.com/ual/en/us/fly...weiss-air.html