it works with these:
Corsair Mac Memory (2x, 32GB, DDR4-2666, SO-DIMM 260 pin)
(Corsair Mac Memory 2x, 32GB, DDR4-2666, SO-DIMM 260 pin)
But be patient when installing them - it took my Mac about 5 minutes (black screen, no sound) until the RAMs were finally recognised after the first switch-on. From then on, the Mac boots again at the usual speed, but the first time after changing the RAM is annoyingly slow.

I used these:
Kingston KTH-PN426E/16G (1x, 16GB, DDR4-2666, SO-DIMM)
Worked like a charm.