the only icons GP has are the theme icons – such as the Hamburger, Search icon, back to top etc.
That option simply removes the need to load a font and instead use inline SVG.
They’re not meant for use in content.
But if I want to insert a SVG now, for example in the content area, I currently use the HTML block from Gutenberg and insert the SVG code there. Strangely enough this code disappears after a while. By the way, the icons at the button also (generator blocks). Very strange (and yes I’m sure I put them in, deleted the cache and the site worked fine, but somehow SVGs disappear)