I've assumed it worked fine on Linux but your comment brought me to this after a quick search: https://bugzilla.kernel.org/show_bug.cgi?id=118721. I've not seen any major issues on Linux e1000e defaults but never pushed it harder than laptop usage. I've occasionally tried to make em(4) TSO work on FreeBSD (it works fine on igb(4)) but gave up due to stalls. Linux has GSO (maybe invented partially due to those issues?) so the benefit is a lot smaller there.

There's a comical change where Intel downclocked DMA to fix some issue and it makes TSO max out at ~700mbps: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin... but they later disable TSO there with https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...