Install obsidian-vimrc plugin. and follow instructions to create .obsidian.vimrc.
Paste the following:
set clipboard=unnamed
unmap <C-c>
iunmap <C-c>
In How to copy with vim mode? - #27 by santi only the first unmap was suggested, but the second is needed for insert mode.
Don’t forget to restart Obsidian after saving the vimrc file!