The following endpoints have been consistently non-operational for the last week.
@Lydia_Pintscher looked over the list and chose a subset that are OK to be permanently removed.
http://data.ordnancesurvey.co.uk/datasets/os-linked-data/apis/sparql
http://statistics.data.gov.uk/sparql
http://zbw.eu/beta/sparql/econ_pers/query
http://zbw.eu/beta/sparql/econ_corp/query
http://collection.britishmuseum.org/sparql
https://bag.basisregistraties.overheid.nl/sparql
https://brt.basisregistraties.overheid.nl/sparql
http://collection.britishart.yale.edu/openrdf-sesame/repositories/ycba
http://bnb.data.bl.uk/sparql
https://www.ebi.ac.uk/rdf/services/sparql
http://sciencesource-query.wmflabs.org/proxy/wdqs/bigdata/namespace/wdq/sparql
https://api.druid.datalegend.net/datasets/nlgis/gemeentegeschiedenis/services/gemeentegeschiedenis/sparql
https://wdhqs.wmflabs.org/sparql
https://linkeddata.cultureelerfgoed.nl/sparql
https://tora.entryscape.net/store/sparql
https://api.data.pldn.nl/datasets/cbs/wijken-buurten/services/wijken-buurten/sparql
https://linked.ec-dataplatform.eu/sparql
https://test-linked.ec-dataplatform.eu/sparql
https://imagehash-sparql.wmcloud.org/sparql
https://data.library.sh.cn/sparql