The MMM vocabularies for Manuscripts, Persons, Organizations, and Places are available as part of the MMM data deposit in Zenodo: https://zenodo.org/record/3667486
Some other vocabularies (not necessarily LOD) for Places were posted to the Digital Medievalist mailing list by Paolo Monella on May 25, 2020:
http://www.landesgeschichte.uni-goettingen.de/roads/viabundus/the-project/
http://atlasfontium.pl/index.php?article=project&language=en
https://www.uu.se/en/research/infrastructure/norseworld
https://www.uantwerpen.be/en/projects/gistorical-antwerp/about-the-project/gistorical-antwer-i/
https://www.nottingham.ac.uk/research/groups/epns/survey.aspx
http://fabricadesites.fcsh.unl.pt/mercator-e/
https://mobilityandspace.wordpress.com/programme/
Tabula Imperii Byzantini: https://tib.oeaw.ac.at/index.php?seite=digtib
Early modern places: https://github.com/culturesofknowledge/emplaces
Credits: Arno Bosse, Charlotte Roueche, Sinai Rusinek