The cause is clearly related to webkit2gtk-4.1. Is no one else having this problem?
Just like Evolution, the package "eolie", a simple web browser for GNOME, also depends on webkit2gtk-4.1, which, as I've just noticed, has also become unbearably slow. So I checked what else I had installed that had the same dependency. This includes, among other things, the Atril document viewer, which has not only become incredibly slow but also formats documents strangely. Since webkit2gtk-4.1 hasn't been updated in quite some time, I assume the problem lies somewhere in the dependency chain of webkit2gtk-4.1. At least Eolie outputs the following via the command line: ** (org.gnome.Eolie:212868): WARNING **: 01:37:25.734: webkit_settings_set_enable_offline_web_application_cache is deprecated and does nothing. [ERROR] 2026-06-15 01:37:48 AdContentBlocker::__on_load_uri_content(): Expecting value: line 1 column 1 (char 0) I have absolutely no idea where to send a bug report. Most likely https://bugs.webkit.org/ . I don't know what to make of what's on https://bugs.webkit.org/buglist.cgi?chfield=%5BBug%20creation%5D&chfieldfrom=7d . In any case, there are reports about GStreamer, and Evolution did indeed display an error message about it. However, as I already mentioned, it only happened once, never again after that.
