I was thinking of GMing an OSR campaign in a setting akin to Dark Albion except it is based on the bronze age instead of medieval Europe, any tips?
One would use RuneQuest, since the default fantasy setting of Glorantha is bronze age.
oh, so I guess a historically authentic bronze age setting has been done?
*edit* not quite, I was thinking more based on the actual history/mythologies from back then
If your French is good, and if you can find a copy, there was Légendes (http://www.legrog.org/jeux/legendes) (later republished as a boxed set Légendes Celtiques (http://www.legrog.org/jeux/legendes-celtiques)), a simulationist rpg from the early 80's. It was historically pretty accurate but had some mythological elements. The system used d20 but was not D&D derived.
(http://www.jdrp.fr/img/items/legendes-celtiques-130.jpg)
For a d20 system that came out during the 3rd edition glut, Mongoose published 'Slaine - the RPG of Celtic heroes (https://en.wikipedia.org/wiki/Sl%C3%A1ine:_The_Roleplaying_Game_of_Celtic_Heroes)' based on the comics.
(https://upload.wikimedia.org/wikipedia/en/8/8d/Slaine-RPG-Mongoose-2002.jpg)
Maybe these two can give you inspiration what to do (or which mistakes to avoid).
I was thinking more centered around Egypt and Mesopotamia.
I was only using Dark Albion as an example for authenticity
also, would a modified Lion and Dragon work?
Then you are in luck ;) because there is also a Valley of the Kings version of Légendes.
For Mesopotamia, Green Ronin published an Old Testament d20 supplement. Not osr but D&D 3e.
don't know French; How hard would it be to modify Lion and Dragon to suit this purpose?
There's Blood & bronze from Cyclopean Games.
https://bloodandbronze.com/
https://www.drivethrurpg.com/browse/pub/9554/Cyclopean-Games
Been a while since I played, but I recall enjoying the game while it lasted. Unfortunately, it was an online group and several members just kind of vanished into the mist, so we never got a chance to continue long term.
Check out HR6: Age Of Heroes for D&D 2nd Edition, a sourcebook for roleplaying in ancient Greece.
GURPS probably has a suppliment, or several suppliments for Bronze Age as well. GURPS Egypt comes to mind.
Dark Sun (AD&D) had rules for stone, and bronze weapons.
One thing you might want to consider is having rules for parrying and dodging attacks instead of D&D Armor Class, since a cient armor was not that great. I believe the Chaosium systems have that.