Found issues with web-ring participant list integrity - some sites went inactive (which is expected I think) and some sites have «disappeared» from list although they active and have ring widget. It seems that the main reason is site renaming, but I suspect that data loss took place as well.
So I'm going to review participants list manually and check what can be done to avoid that. Registration will be closed during maintenance works.
There are sites that I was able to find using Google that mentioned null ring participation and have widget on site, but they are missing in the list. If you cannot find yourself in participant list, please notify me in neocities.
Decided to move nullring backend to Render PaaS to reduce maintenance burden.
Refactored ring backend. Now it should support custom domain by examining URL it was redirected during site verification.
Changed backend location again and cleaned duplicates from list.
Moved away from DDNS for now as I regularly forget to renew domain and no-ip have policy to lock expired domains for month.
Fixed ring subscription code that allowed to register multiple times and cleaned the member list of dupes.
Found kinda bug in ring widget code (which is actually not a widget bug, but an design drawback). When site is still on neocities, but has custom domain, widget fails to find it in the list and display correct neighbors.