For details on the “new” /allguis page.
This is something we had before, but now fixed up to work properly on latest release.
When you open the web gui with /allguis as path, for example http://192.168.51.1/allguis it will load a special page that will cache all the plugin resources in the browser (assuming the browser is able to do such things)
So next time you load up the regular webgui, those plugin resources should be in cache and thus the web gui loads a bit faster.
The intention is to help with bluetooth connections which are very slow. So you load up the bluetooth dedicated web url http://192.168.50.1/allguis and let it be while it fetches all plugin stuff.
Note that the resources are versioned, so cache is valid only for 1 specific version/build.
After an update, this step is required in order to cache the whole plugin resources again.