Yes but you will need to somehow track the users. You can let each user subscribe to a unique topic or get the Firebase token and send to the token instead of the topic.
is this solution ok?
send the notification text like this:
SERVER SENDS
title = "[45] Amouncement"
body ="Thank you for joining "
* where [45] is the user id
so on the App :
B4X:
Sub fm_MessageArrived (Message As RemoteMessage)
Dim user As String = Message.GetData.Get("title") '[45]Welcome
Dim userid As String = user.SubString2(user.IndexOf("[")+1,user.IndexOf("]"))
Dim cleantitle As String = user.SubString(user.IndexOf("]")+1)
if (userid="45") then
Dim n As Notification
n.Initialize
n.Icon = "icon"
n.SetInfo(cleantitle, Message.GetData.Get("body"), Main)
n.Notify(1)
endif