I must say, this is a fun one

Steps to reproduce the error

(...hopefully, see [1])
TL;DR: open the link https://lobste.rs/domains/thephd.dev and see if it loads while logged out

Open lobste.rs if not already open and login
Search for a recent blogpost by thephd.dev. For example "the cost of a closure in c" (direct link to search)
Click on the article, check that the link, story page and lobste.rs comments load fine
Click on the domain to view other stories submitted to lobste.rs that belong to the same domain
Click on some other domain and see if those load
Log out and repeat the above steps and see if there's a difference

Expected behavior

The domains page in general and in particular for the specific website should load without issues.

Actual behavior

The page tries to load and then fails with a blank page and a 500 Internal Server Error
It loads when logged in but not when logged out

Other details

[1]: This issue didn't happen in my default browser (Firefox 146.0 (aarch64)). However, when testing on a New Container Tab, Fresh Private/Incognito Window, Vivaldi (7.7.3851.48, arm64), Safari (26.1 (21622.2.11.11.9), the page doesn't load at all and throws an error. I also checked on few android browsers (vivaldi, firefox) and those don't load as well. It was only while writing this issue I realized I'm logged in on my default browser and sure enough, it loads fine after I logged in from firefox browser on android. Turns out, logging out of my default browser made it break as well... (thanks for the tip in the bug report description!)

Another thing that's particularly of note is that the link errors without ever loading the lobste.rs html/css. This makes we wonder whether this is related to a reverse proxy trying to block nefariously crafted links (a while back, another website accidentally blocked search results page when the search query contained cyrillic or similar characters). I tried searching for similar issues but apart from some recent change to domain pagination I wasn't able to find a similar issue.
Checking the Network requests in Developer Options didn't show anything useful (but maybe I missed something)
I also wasn't able to reproduce this error on another domain I tried (eg: buttondown.email)