9. Type `C-u C-x v d' (that is, add a prefix argument to `C-x v
d'). The following prompt will be displayed:
VC status for directory: ~/tmp3/project1
At the prompt, accept the command by pressing the <RET> key. The
second prompt will then be displayed:
Use VC backend:
This should be fixed in Emacs 28.2 released in September.
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=51800 says Emacs
29 only, but it's been backported.
Since you are not seeing the exact error for some reason, it's
possible that your problem has not been fixed still. But try
Emacs 28.2 at least.
If the Emacs maintainers say that they have verified (by
following the steps needed to produce the problem in Emacs 28.1)
that the problem reported for Emacs 28.1 has been fixed in a
later release, then that should complete this process.