It depends.
I would say an AV on Android adds only limited value, but it's still adding something.
I would say the added value is real only if you do a lot of experiments on your smartphones (installing random apps from unknown sources is included), but there are a lot of things you can do that are possibly better then the AV.
You might use secondary profiles (like work profile with shelter or private space) to reduce the damage if you take a malware.
You can set private DNS (DOH or DOT) or even filter some DNS requests (Mullvad DNS are free to use and do this for you, or you can use other apps that will take your VPN slot).
The AV might help you if you casually gives permissions to all the apps you install and might detect if your partner install some app to monitor you, but if you are the sole user of the phone, the main risk is just what you install from unknown sources and what you browse.
I am not saying AV are useless per se, I would say that they add very little value to an Android OS, especially GOS.
Having good habits is a safety net more robust than the AV, that might tell you that something is wrong only after something went wrong.
Some AV might also inspect web traffic, in that case they might add some value at the cost of battery usage.
Also, about web traffic, Vanadium has an option on that regards, but I never tried.
The equivalent on Google Chrome is basically sending a copy of the traffic to Google, I am not sure if this is working the same in Vanadium because I never enabled that.
Maybe someone else can help us with this.
This basically sums it up:
User2288 Just add a good firewalling/adblocking ability to GOS and be mindful of your practices and you are as secure as having an antivirus