I started using the learn2 theme by Grav.
Since it's got the logo and some custom stuff, I've just modified it a little bit:
To change the svg logo on the theme I had to hop into the www/user/themes/learn2/templates/partials folder and check for the logo.html.twig file.
To delete the Grav mark, I went into www/user/themes/learn2/templates/partials sidebar.html.twig and deleted the footer section id.
To change the favicon I changed it in here: www/user/themes/learn2/images
I will leave some other tweaks for later.