What about if you use:
git clone --single-branch --branch stable
This results in the same issue. Why would adding --single-branch make a difference?
For the record here is the JS error that’s breaking the rendering of the site
TypeError: t.addKeyboardShortcut is not a function _discourse-assign-247a26621189a1714b70bd1b1b82b3a6fecb3b42abd693e59778ada8c009780f.js:732:8
initialize _discourse-assign-247a26621189a1714b70bd1b1b82b3a6fecb3b42abd693e59778ada8c009780f.js:732
withPluginApi _application-ed0ac692ab93afd4124933b80c2b9e44bca02a77b73366b3e67eef88e883e0db.js:21205
initialize _discourse-assign-247a26621189a1714b70bd1b1b82b3a6fecb3b42abd693e59778ada8c009780f.js:743
initialize _application-ed0ac692ab93afd4124933b80c2b9e44bca02a77b73366b3e67eef88e883e0db.js:7258
jQuery 21