This workflow is tied to KDE Plasma's tagging feature. Moving away from KDE Plasma would likely mean abandoning parts of this workflow altogether.
It looks like these tags are stored in filesystem xattrs themself, not in dolphin or kde metadata. That is, even if you load up gnome's file browser, or another file browser, it should still be able to read them.
Nope, it looks like the tags used are KDE specific, even though any software could theoretically implement support for reading and writing them.