Don't get me started on Google! Hangouts, for whatever reason, never got iOS multitasking support like being able to use it in a side panel (and if I recall correctly, the multitasking features got to iOS long before Google started abandoning Hangouts or whatever they're doing with it now). Though to be fair, I really think Apple should have found a way to do this without a requirement from app developers. I don't think it's an impossible task - just look at what Samsung DeX can do on Android without explicit support from existing apps (even if it isn't perfect,).