It uses Android Web view which is essentially just Chrome without the interface, and is entirely proprietary. It suffers from all the drawbacks of Chrome based browsers with the added problem of being an Android component so out of much, if any, control of the developers.
This app should not be a serious consideration for anyone who is privacy or security focused. The very first thing a secure browser should be providing is it's own rendering engine. Even providing it's own chrome based rendering engine would be more secure than this.
Also in terms of extensions, as it is Chrome based it's extensions such as uBlock will have the same privacy breaking restrictions as the rest of the chrome ecosystem with manifest v3 which favours Google's advertising business over user security and privacy.