Thanks for your feedback. Part of the reason that Endless is a great OS is because it is built upon great open source software. Open source software usually only becomes great through the involvement of the wider user community, especially when key developers have limited time to work on it. So if Twitch is important to you, I’d definitely encourage you to make a small contribution to the GNOME Twitch community through reporting the difficulty you have faced with it, even if the software has not seen significant recent updates.
In terms of extended administration powers, I’d encourage you to further explore podman and toolbox, included in Endless OS. To give a clue of its capabilities, take a look at how Mariadb/mysql can be taken directly from Fedora and run on Endless. Or see how gnucash can be taken from Ubuntu in order to overcome a limitation with the flatpak version. The containerisation here provides a nice compromise between the high level of robustness offered by Endless OS’s unique design, while also giving you a big dose of freedom inside your own sandbox.
And feel welcome to let us know what other tasks you are having trouble with on Endless OS so that we can consider improvements for the future.