With Avast deactivated, I succeeded in reinstalling git-lfs (with considerable problems, see below).
However, starting today, when I try to do a git pull on the WSL with Avast (free version) activated on Windows 10, Avast kicks in and tells me that git-lfs is infected with ELF:Agent-AJO after which git-lfs becomes unusable (even when deactivating Avast).
The following problem suddenly turned up on my Windows 10 Laptop: I have been using the Windows Subsystem for Linux for years, and I've used git-lfs (git large file storage) on the WSL for several months now.