General best practice IMO is any navigation link/button that is just some permalink like a profile page should be an a tag to support natural browser interactions like open in new tab or bookmark link, it also helps crawlers index your app if the interface in question is some sort of public directory you'd like indexed and has SSR. Only navigation based on ephemeral state (submitting forms etc) to things nobody would typically share a link to (logout URL, submit button going to a thankyou page) should be buttons.