Problem updating rss feed

I have been using tt-rss to fetch this feed https://discourse.devontechnologies.com/latest.rssfor quite some time, but this rss feed stopped updating a while ago. When using curl -l and the above URL I am getting this error: “SSL certificate problem: unable to get local issuer certificate” on the command line but no problem with curl -I -k. I cannot follow the suggestion to update my CA certificates, because I have no admin priviledges on the site hosting the tt-rss installation. Any suggestions how to get the rss feed working again?

See DEVONtechnologies | Problems with Security Certificate