Making Flatpak available on SFOS was mainly to get an access to updated web browser. I am using and contributing the code to Angelfish which is default browser for Plasma Mobile. It is based on QtWebengine and is able to run on Wayland. I would recommend to use that and, if something is missing for you, consider writing the corresponding feature. Iff SFOS gets updated Qt, it will be relatively easy to port Angelfish to Silica (or maybe even better, make Kirigami/QtControls style for SFOS that would allow to use Kirigami apps unchanged).
With a more modern wayland protocol support we could also have firefox running on it. In some form at least.
But they said they might fix that (the protocol).
Accessing context menus for angelfish only worked from tabs view in my case.
Thanks @rinigus for your help.
Otherwise, playing a song on youtube and switching to another tab was working fine a few hours ago.
And I just redid the manipulation, it cuts the sound.
In the meantime I modified some scaling / DPI settings but it would surprise me that it was linked to that. Do you have any idea for that?
One more way, as found by @leszek: you could use one finger to fix the application, let’s say hold in the middle of a screen. With the other hand, swipe from left or right. Then SFOS will not swipe app out, but will forward the gesture to the app and open the menu.
As for changing the tabs and listening on the background - it maybe related to some memory management of tabs. As for why it kicks in, I don’t know.