this is only available at digitec and not in germany

Other countries do not necessarily have nationwide router freedom. Since the standards were not necessarily uniformly defined either, AVM developed a so-called "international version" for various countries (except Germany), which harmonises with the Internet connections abroad. Since an international version needs considerably more adaptation than a German version, updates have also taken longer.
But now it was decided to combine the standards from the German and international markets. With the current FRITZ! lab version, there will be only one version for all models in the future - a worldwide FRITZ!Box. This will eliminate the difference between international and German. However, the update supply is to be continued. The other country standards are now so far advanced that the adjustments in the future will probably be of a lesser nature.

20849818 is the international

AVM FRITZ!Box 6850 5G, International
20002928

see Christa's answer,

digitech 16771721 is AVM article 20002928 = AVM FRITZ!BOX 6850 5G International Edition (20002928)

digitech 20849818 is AVM article 20002914 = AVM FRITZ!Box 6850 5G Germany

at galaxus.de the search does not show 16771721

You can enter the number in the Digitec search box or in Google so that it shows you the item. It works for me for this item (20849818) and the supposedly same item (16771721).

there is no article 16771721