Sounds like - I already found something similar, but I'm not so deep into Eclipse to hack it.
EGit version released with MCUXpresso IDE 5.4.0.201906121030-r and apparently it is not possible to install release 5.6.0 because of a dependency issue:

Of course we don't want to uninstall "MCUXpresso IDE additional plugins"! That turns out to be com.crt.lpcxpresso.feature.product.feature.group:

The singificant lines are:
Cannot satisfy dependency:
From: MCUXpresso IDE additional plugins 11.1.0.201909161352 (com.crt.lpcxpresso.feature.product.feature.group 11.1.0.201909161352)
To: org.eclipse.equinox.p2.iu; org.eclipse.egit.feature.group [5.4.0.201906121030-r,5.4.0.201906121030-r]
I googled a bit, but I can't find a workaround so far.