It’s less that it’s broken and more that it hasn’t been implemented yet AFAIK.
To be fair, I would not expect someone using a wayland WM and urxvt to use the mouse to copy-paste.
I understand. I’m not using sway and urxvt as someone more skilled would do. I’ve Made this config some years ago to try but nowadays I’m not doing computer things anymore but I’ve kept this config because it’s light, fast and it’s simply working. So basically, today I’m just copying my passwords from pass in urxvt to my webmail in Firefox with my mouse for checking mail …