No, afaik every alternative frontend that still works with age-restricted videos works by letting you sign in with a Google account (which defeats the point). I’ve tried a few.

I just make an account for just the age-restricted videos. FreeTube still works for me for non-age restricted videos (if it doesn’t for you, try changing VPN countries a few times—also you need to restart FreeTube every time you change VPN servers, otherwise it doesn’t work from the new server, idk why).