In Victoria Australia under UGLV...
We have our National Flag and State flag. I've seen in Lodge Garibaldi, they put the Italian Flag up. On Burns Nights, i've seen the Scottish Flag. Both in Lodge and additional to the first two. In Military Lodges, Ive seen the army, airforce and both Navy flags. In a Vietnam Memorial Lodge, I've seen the South Vietnamese flag....
As far as i can remember, our Constitution is silent on flags, its a question of convention rather than prescription or proscription.
If I was visiting and saw a religious flag, I might shift on my seat and curiously ask why, but being a good guest would never comment..
In a similiar vein, I've never seen a Muslim bro comment on the absence of a Koran. For me, what is on the heart is in the heart, regardless of the VSL or flag displayed.
All that said, if it appeared in a craft lodge i am a member of (or indeed known as a regular visitor and friend) i would 100% quietly comment to the Master, IPM or DC (Marshall) and question its appropriateness. At the two lodges I am a PM in, we have Christians, Muslims, 1 Jew, 1 Buddhist, 1 Hindu and some who are none of these and would say we are dangerously encrouching on BOTH no religion or politics rule in displaying a flag of faith. Indeed such fags can also be politically charged....
"... whilst in the Lodge by abstaining from every topic of religious or political discussion...."