On Linux there is Falkon. Windows too. (QT WebKit) And the reason I won't use this will likely be the same as Falkon. Missing plugins etc. Other than that they are fine. Bitwarden has a desktop app. (Electron? Dunno but it would be ironic) But no auto fill ability. Darkreader? Nope. There may be some limited adblocking, but no greasemonkey type functionality.