UPDATE: The suggestions below might work, but what about just locking Brave in the Finder? That is, go to Applications, right-click or control-click Brave, and in the ensuing window, check the box next to Locked. In theory, that should prevent changes.
Also, it looks like the devs heard the users’ complaints, albeit too late for those using older OS. This is what I get in Nightly on Big Sur, now:
–End UPDATE–
It might be worth trying command line switches. Here’s a link to my source. Here are two promising ones:
-
--check-for-update-interval- How often (in seconds) to check for updates. Should only be used for testing purposes. -
--disable-component-update- no description
I tried using both (20 years in seconds for the first) and they didn’t return an error, but I don’t know that they worked, either.
What I’d suggest is writing a tiny AppleScript to issue the command you want to try:
open -a 'Brave Browser.app' --args --check-for-update-interval=630720000 (that’s 20 years expressed in seconds); or
open -a 'Brave Browser.app' --args --disable-component-update
The script would look like this (use Script Editor 
- should be in /Applications/Utilities):
if application "Brave Browser" is running then
tell application "Brave Browser" to quit
do shell script "open -a '/Applications/Brave Browser.app' --args --disable-component-update"
else
do shell script "open -a '/Applications/Brave Browser.app' --args --disable-component-update"
end if
tell application "Brave Browser" to activate
You could do both commands by adding one after the other like this:
open -a 'Brave Browser.app' --args --disable-component-update --check-for-update-interval=630720000
I tried that and it didn’t throw an error, but, again, don’t know if it worked, either.
If you copy and paste, make sure no stray formatting codes have been included. Also, I use Nightly, so if I left that word in the app name by mistake, just omit/delete it.
Once you’ve written that in Script Editor, save it, then also save it as an Application some place you’ll remember, then go to that folder and drag the new Application to your Dock and use it to launch Brave instead of clicking Brave’s icon (every time). I do this with a script to make the cache tiny and it works great.
If you need more help, let me know. If it works, please also let me know.