Maybe @falco is right. I thought about using link icon. At least then it is not a rare glyph we barely use anywhere else.
Like @falco’s post above if you prefer link glyph.
edit: this is clearly never going to be resolved to anyone’s satisfaction. (I’m not saying I felt there was an obvious “winner” anywhere in here, either.) So, in the interest of less bikeshedding, I am making the final editorial decision that we’ll use the link icon there, since these are absolutely links, and that thematically ties together the link button action, and there’s no arrow direction to worry over 