Can't install an older Unreal version on an older Intel Mac

Because of a PC hardware failure, I got out my older 2018 intel-based Mac running Sequoia, which I used to run UE 5.5 on. After installing the Launcher, I find that I cannot install any version of UE. When I press the Install button, nothing happens, regardless of the version of Unreal Engine. Tailing the Launcher’s log, nothing is being written to it when I press Install.

I’ve been building the engine from source today, but I am sure I’m going to run into trouble with the Launcher again when I want to install some of my purchased plugins.

Has anyone got any suggestions for how I can get the Launcher working once more? I suspect it something to do with the intel/M chip changes, but I don’t know how I would get an older version of the Launcher to try out.