Cohost has a terrible combination of a giant register button and hidden log in button on the landing page and killing all your other sessions when you sign in on a new device.
There's not a native app so every time I want to access cohost on my phone after using it on my PC I have to: 1) ignore the big ol "Get Started" button and open the hamburger menu to select log in. 2) Switch out of the browser and open LastPass to unlock it. 3) Return to the browser and tap the fields until LastPass feels like keeping the fill option on screen long enough to press and 4) close LastPass.
I seem to remember that at one point in the past, Tumblr had a registration form right on the landing page, but if you entered the email and correct password of an existing account and submitted the form, it just logged you in without further hassle. It was also set up to where a password manager in the browser would just autofill them. I liked it.