Which analog four OS work with Overbridge?

Hello,
Do you know which analog four OS work with Overbridge 1.15?
And is it still possible to download any of them? I cannot install Overbridge 2 on my OSX El Capitan.
Thank you

…in principle works each os update with the actual ob from around that time…
ob was invented FOR the a4 in first place…everything after was “just” adding on to this…

i’m afraid u stuck inbetween here…
so ur a4 is on latest firmware…no idea if older ob versions can adress that…
while most newest ob version that would suit ur a4 best and for sure, won’t work on el capitan…
hmmpf…that’s a classic catch 22…

so first try, i’d say…look for the ob version that was adapted to el capitan…not sure there was such thing…el capitan is soo long ago by now, if so, it was the very first ob version that did the trick…

downgrading a4 is no option…and a proper version of ob that worx on actual status remains the goal…

so, start thinking about mojave…ob adresses back fine to that…
and all el capitan macs are capable to step forward to mojave…

but i’m no big firmware os whatsoever pro…let’s see who’s showing up here with better solutions…

Thank you reeloy,
I’m on A4 1.24. It works with fine Over Bridge1.15, but I think I loose A4 OS improvements.

And “yes” you miss out on all the firmware improvements since 1.24c (which are a lot when you check the latest firmware release notes listing them all).

So many? Hum… So I’ll have to install Sierra… I always afraid of that.