Meanwhile I made that the 8 Sikh temples in Belgium are in OSM as building=temple (plus place of worship). They aren’t small.
Not all chapels are small. The difference between a chapel and church is that churches were consecrated as parish churches. Chapels were not. In a monastery, such a chapel can be quite large. But there are others too. For risk management purposes, I can understand that there is a difference between a small chapel that can accommodate 10 people and a large chapel that can accommodate 70 or more.
Currently, I see a whole movement in the municipalities to deconsecrate churches that attract too few people and are too expensive to maintain. I estimate that 70% have been repurposed as community centers or something else, or they are being demolished. I try to follow this around me and delete place_of_worship, but that is not easy.
In Wallonia, there are also quite a lot temples of Antionism. They are not so small. They are mapped as temples, churches, chapels, or yes.
OpenStreetMap