Rav Bunim Shreiber, Rosh Yeshiva of Netiv Daas and rabbi in Ashdod, has paskened that witnesses at a wedding must remove their masks, or lower them to make the face visible, during the chuppa. They must do so even though it means breaking the Ministry of Health guidelines (for a short period of time).

Rabbi Shreiber explains that by wearing the masks, the witnesses cannot be fully identified by other people. Wearing the mask would make it difficult, if not impossible, to be "meizim" the witnesses. Viable witnesses must be potentially impeachable as "plotting witnesses", eidim zomemim. Yet with their faces covered, nobody would be able to impeach their testimony by saying they were spotted elsewhere, so the testimony shouldn't be valid to start with. Thus, the masks must be removed to make them potentially impeachable.

Rav Chaim Feinstein, the Rosh Yeshiva of Ateres Shlomo, disagrees and believes that testimony requiring theability to be impeachable is only a law found in the laws of Choshen Mishpat, financial laws, and is not found discussed as a factor in Even HaEzer - the laws of family such as marriage and divorce.
source: Hamechadesh

I would add that the Gemara talks about the rules of eidim zomemim in regards to issues of the death penalty, not just financial matters. Also with regards to transgressions that would obligate one in receiving lashes. So I am not sure this categorization is accurate, but I don't know enough about the application of eidim zomemim to argue this reasonably.

I would also note that the witnesses are supposed to be witnessing Reuven marrying Sarah, or whoever. In many weddings the bride, Sarah in our example, is covered by a very thick veil that is not see through. I have almost never seen the witnesses look under the veil, have the bride lift the veil for a moment. I do know one person, and have seen it myself, who has been witness at a number of weddings, and he is always careful to insist on having the bride lift the veil so he can confirm who the bride is, that she is the person that the groom is supposed to be marrying. But that is uncommon. I find it interesting that these rabbonim are debating the mask that partially, and only for this hopefully temporary period of time, covers the faces of the witnesses, yet make no mention of  the mask, the veil, that regularly covers the entire face of the bride.