Creating a browser from scratch is a monumental task, ladybird is such a project which has been in progress since ~2022, and will probably take another couple before it's at beta. Optimistic release is 2028, or ~6 years of development.

I've moved to schizofox (NixOS) but there are plenty of other forks available which remove telemetry and other default behaviours from Firefox.

Chromium forks are another alternative however due to chromiums dominance in the browser space I'm reluctant to shoutout any forks.