Translation of teletext:
Protestors arrested at KTH
Three people have been arrested and some 20 have been detained after a protest at the Royal Institute of Technology in Stockholm.
According to police they are suspected of for instance crime against masking ban, disobedience against law enforcement and vandalism.
Protestors at the scene declare to SVT that they have protested against Israels warfare in Gaza in connection with the fact that the Christian Democrats' party leader Ebba Busch visited the school.
Also at Lund University there are ongoing protests against the war in Gaza.
The laws I can find seem to only care about public context and not the actual mask in questions, aside from allowing for religious facial coverings, if the cops decided that a medical mask was being worn to conceal your identity at a "public demonstration" that is a "disruption of the public order" or at imminent risk of becoming that, they could probably charge you with the crime.