Use aho bakaup with Fern - aiya000/aho-bakaup.vim GitHub Wiki
Use the following Vim script to use fern.vim instead of Netrw on BakaupExplore
command:
function! s:init_bakaup() abort
command! BakaupExplore execute printf("Fern %s", fnameescape(g:bakaup_backup_dir))
silent! delcommand BakaupTexplore
silent! delcommand BakaupVexplore
silent! delcommand BakaupSexplore
endfunction
augroup bakaup
autocmd!
autocmd VimEnter * call s:init_bakaup()
augroup END