Not directly something to do with Batocera, but some people may have some compilation to make for kernel 4.4
and just have a PI3B + to their disposition. In general Raspian Jessie (last version 05-07-2017) will not boot on the plus version. The PI3B + was introduced with Raspian Stretch (first version 13-03-2018) with kernel 4.9
But if you have like me, something to compile in 4.4 under the plus version, after backup of the SD card, you can update Jessie, making following 3 operations under an old PI3B without +
sudo rpi-update ef7621d91cb58ccc856c3c17ddda28685edd23f3
sudo dpkg -i firmware-brcm80211_20161130-3+rpt3_all.deb
After, Jessie will work on an PI3B and a PI3B+.