I have a layer (possibly external service) that causes projects to take up to 30min to open.
Please add a process to ArcGIS Pro (on 3.5.1) to sanity check loading times.
If a source causes a project to take longer than a few seconds (or some reasonable time) to load, ping the user and asks if source should be removed, marked inactive (red !) or keep waiting.

Some data sources can be slow, but having to wait 30min before you can troubleshoot is not the best use of time.