Is there a browser in which you can block all sites except for a specific list?

Question

Browsers

I searched for a firewall but did not find the right one (free), through a router is not an option

Answer 1

in the connection settings (in the browser)

we start up the necessary / specified domains along the usual path (without using a proxy)
and wrap all the rest on a non-existent proxy.
more flexible can be configured via .pac file by specifying the file in the browser settings
https://en.wikipedia.org/wiki/Proxy_auto-config