The yearly (since 2012) FOSS4G-NL conference will be held in Middelburg, Province of Zeeland on 13 (workshops) and 14 (tracks) September 2023. Location in scenic medieval buildings in the heart of Middelburg, like the Abbey, a former Premonstratensian abbey. Co-organizer and hoster: Province of Zeeland (many thanks!). Not far from Belgium as well!
For more information, see: https://foss4g.nl
