It just happen now that when visiting https://forum.openwrt.org, hostname mismatch error is shown in Google Chrome.
Here's the report on SSL Labs: https://www.ssllabs.com/ssltest/analyze.html?d=forum.openwrt.org&s=139.59.210.197&hideResults=on&ignoreMismatch=on
It is great to see https://forum.openwrt.org is using Let's Encrypt issued certificate, which should allow multiple Subject Alternative Name to be listed so the same SSL certificate is good for both forum.lede-project.org and forum.openwrt.org.