In the end, I installed a new Windows 10 VM, under which RM 9.1.3 works perfectly well.
I doubt it will work fully under Windows7, since webview2 is no longer supported under that OS. Thanks to @kbens0n for pointing that out.
For completeness… in case anyone else is dealing with it… I also installed Wine and tried to run under it. It worked just the same as Windows 7 with the Windows version set to that OS… i.e. not! With it set to Windows 10 I think it could be made to work but I didn’t want to fool around any more right now. At least under Wine I get messages telling me which dlls are missing. It needed Windows.System.Diagnostics.PlatformTelemetryClient, which is in my (real) Windows 10 distribution. I imagine it can be made to work with some effort but I didn’t know where to copy that dll.
Why so much effort to avoid Windows 10? First, because I use a lot of VMs and Windows 7 is the last version, which ran well on a small VM for me. Second, because I’m trying to get out of Windows entirely.
Thanks everyone for the help.