UI

Changing the floating window to a side window

To make the :LspInstallInfo window behave like a normal window instead of a self-closing floating window, you can include the following snippet in your personal configuration:

function! s:deregister_autocmd() abort
    " Disables the self-closing behavior of the window
    autocmd TextChanged <buffer> ++once autocmd! LspInstallerWindow
endfunction

" For a right-aligned window
autocmd FileType lsp-installer wincmd L | call s:deregister_autocmd()

" For a left-aligned window
" autocmd FileType lsp-installer wincmd H | call s:deregister_autocmd()

Changing the border of the popup window

Provide the border style you'd like during setup:

require("nvim-lsp-installer").setup {
  ui = {
    -- The border to use for the UI window. Accepts same border values as |nvim_open_win()|.
    border = "rounded"
  }
}