It's a new one to me also. It's apparently from the folks who made Opera, which is an excellent browser but which was recently redone with Chromium (Like Edge, Brave, Chrome).
No idea about security, at least so far.
The CEO of Vivaldi did not kill Opera, the company was taken over by a Chinese consortium who killed the original Opera. That is why Jón S. von Tetzchner is developing Vivaldi with his own resources to replace the old Opera
Indeed,
In November 2016, the original Norwegian owner sold his stake in Opera Software company to a Chinese consortium named Golden Brick Capital Private Equity Fund I Limited Partnership for $600 million.[46][47][48]... Versions with the Blink layout engine have been criticized by some users for missing features such as UI customization, and for abandoning Opera Software's own Presto layout engine.[92][93][94][95] Despite that, versions with the Blink layout engine have been noted for being fast and stable, for handling the latest web standards and for having a better website compatibility and a modern-style user interface.[96][97][98] (https://en.wikipedia.org/wiki/Opera_(web_browser)#History)