How to run a program from an old generation?

[Γυψ <gyps@member.fsf.org>]

Dear all,

I currently have an issue with nextcloud-client segfaulting in the
current guix environment. Until this is fixed an option were to switch
to the old generation where it still worked, start it and switch back to
the current generation.  Is there an option to run a program in a
specific generation without completely switching to it? I didn't found
any so far.  I know that's a real hack but at least that way I could
have my files synchronized without too much effort until the bug is
fixed.

Another question I have is: can I install version 3.1.3 of
nextcloud-client in the current environment (without switching back to
some old commit)? When I try to do so, I get

> guix install: error: nextcloud-client: package not found for version 3.1.3

because version 3.1.3 was replaced by 3.2.0.

Cheers (and a happy new year!)

Alex