I’ve used Namecheap as my domain registrar for years now. Simple, efficient and most importantly, no upselling
If you want to host your new domain on tumblr, here is the DNS record. Make this update registrar side as soon as possible, even before going to tumblr because it takes a few hours to ‘kick in’
After this addition, head over to tumblr, create a new blog (name doesn’t matter) and if enough time has passed you should be able to edit the blog and choose your custom domain name as your URL.
Seems like these is a missing link in this process but it is the way it works.
Type A
Host @
IP 66.6.44.4
Type CNAME
Host WWW
Target domains.tumblr.com