It may be "normal", but it's not okay. At least for Firefox, there is a detailed guide published by Mozilla to disabling all of the huge number of "automatic connections" made for "telemetry" (a euphemism for surveillance), updates checking, support for their own/partner cloud services, captive portal & network accessibility detection, etc.:
https://support.mozilla.org/en-US/kb/how-stop-firefox-making-automatic-connections
After following that guide, in theory there should not be any connections made on startup. If there are, the list will be much smaller and more managable to track down what's still happening.
I have no idea if Brave has similar functionality. Brave is not really a privacy-respecting or -oriented browser, just somewhat misleadingly marketed as one. If you want to track down what it's doing, you could start by switching all the preferences as private as you can get them (including turning off their BAT cryptocurrency stuff) and see if you get a more managable list to investigate.
