I did the most recent software update and I couldn’t get gVim to work anymore. I did some digging with my limited knowledge of Linux and eventually got it back.
It seems that gVim is in the vim-gtk3 package. I think the problem is that version 2:8.1.0875-5 has dependencies for vim-common, vim-gui-common, and vim-runtime, all for version “(= 2:8.1.0875-5)” rather than “(>= 2:8.1.0875-5)”, and the Software app installs version “2:8.1.0875-5+deb10u3” … which is not equal to 2:8.1.0875-5. Thus, you have to “downgrade” those packages to get gVim to install. Don’t quote me on this (I did the updates then closed the terminal session so I lost the history) but the process was:
sudo apt reinstall vim-common=2:8.1.0875-5 sudo apt reinstall vim-gui-common=2:8.1.0875-5 sudo apt reinstall vim-runtime=2:8.1.0875-5 sudo apt reinstall vim-gtk3