Install it over 0.8.10. (This is the same file as the 0.8.11-rc1 test build, so seeing "rc1" in your log is normal.) One crash fix: a friend who had just changed their face could crash the other players' games (the host's, in the report) as they came into view.
It still uses protocol 35, so it plays with 0.8.9 and 0.8.10, but the fix works only in the games that have it: everyone should update, the host most of all.
What changed
A friend who had just picked a new face in the game's face editor (a preset, for example) no longer crashes the other players' games when they load in nearby. Their face showed no body shape values, and the game read past the end of the empty list as it built that friend's body. Now a missing value counts as no change, and the friend still shows their new face.
Known issues
If both of you hit the same enemy within the same instant, one of the two hits can still be lost.
The rest are as in 0.8.10: friends' faces untried with LooksMenu, the stand-in's grenade not shown in its hand during the wind-up, Dogmeat squatting on the joiner, a friend's parked frame taking a moment to move when first synced.