Brussels chess you can simply turn up to 5
Bruxelles 2
Halle 2
Other communes and towns 1
About this page
On these entries a page says in so many words that visitors may come. The Muntpunt library near De Munt keeps its Wednesday chess afternoon free and without registration, for any age. The Ixelles Chess Club writes that its weekly friendly tournaments, the Tuesday blitz at the Toots Jazz Club and the Saturday rapid, are open to all, with no need to belong to a club; a small contribution covers sets and clocks.
South-west of the city, both Halle clubs say that guests are welcome: the Dworp club on Friday evenings at 't Oud Kasteel and De Zwarte Dame on Saturday afternoons. Many other clubs in Brussels let a visitor in for a first evening, but their pages do not say so, and they are not listed here until one does. It is wise to check the evening on the club's own page before travelling.