Weapon options range from K1 combi rifles and flash pulse, to Boarding Shotguns, or a Spitfire for additional SWC along with the usual pistol on all profiles. Martial arts 4, CC 21 and a DA close combat weapon on all profiles makes them very adept in melee. The Hacker also has access to all the advantages of an EI hacking device plus.
Note that with their high WIP Umbra are often better served with Flash Pulse or a hacking program than shooting should they have the option.
Umbra have standard armor and above average BTS but will go down to dedicated fire. Mimetism, V: No Wound Incapacitation will help to keep them up a little longer and turn firefights in their favor. Don't forget dodging though, something they do well with 13 PH and Kinamatica to help them get out of harms way.
The Umbra have higher WIP than BS meaning the K1 Combi and Flash Pulse Umbra will often want to flash pulse on ARO.
Meanwhile the Hacking Device Plus Umbra has access to Cybermask and can use it to move through dangerous areas of enemy fire or even through the trigger area of a mine, the dreaded nemesis of all V: NWI models.
All Umbra also Engage at a larger distance which can some times catch enemies off guard and once in melee they are very likely to win.
Though you have Forward Deployment level 1, it is not always best to use it just because you can. Always select a spot that lets the Umbra safely do their job, not just the greatest distance forward. They are a significant investment of points.
An umbra is an excellent choice for a model with G:gnemonica to jump into, especially the hacker version.
The Umbra fear shock weapons, and mines which force them to dodge when they would much rather be laying down fire. Umbra will falter to visor units or direct template weapons provided the user is not close enough to be Engaged.
The longest range weapons an umbra can bring are still fairly short, so try to take them out from 32" or more.
In general the Umbra is a large point investment that wants to do work on the active turn. It will go down to more expert shooters, lots of dice, or templates, but be sure to send something in with good enough stats to win the fight. If you can, try to avoid fighting the Umbra with AROs, as they have better stats than most models and weapons to let them win most fire fights or melee battles.
Umbra make a good aggressive lieutenant option but are better used as dedicated killing units or button pushers. Generally an Umbra is not a good "drop in" piece. You should have a plan for them in the list. That plan might not need to be more than "bring a hacking device" or "provide a unit with good CC" but it should still be there. The K1 option offers good armor cracking that also can kill infantry, the spitfire is a dedicated anti trooper piece, and the Hacker can use cybermask to push well into enemy lines to make good use of its shotgun or melee.
In the Onyx sectorial umbra can be part of a core unidron link. There are two real schools of thought here. You can choose the hacker is chosen to use the Unidrons to move up field and dominate low visibility parts of the board. The K1 and Spitfire options like the extra dice and BS of a unidron link and will be happy to use it to try and win uneven firefights.
Important note for Onyx: you CAN put an umbra Legate in a Rodok link but doing so causes problems. Without access to super jump, the Umbra will often be limited to idle when the rest of the link wants to jump and can fall behind quickly or cause movement problems for the whole unit.
Umbra should use their forward deployment only if it gets them closer to their objective, and probably skip it all together if going second. Because they are expensive peices, more than 10% of a typical army, the enemy will look to remove them on their own active turn before the Umbra can cause too much damage. Try to game out where they will move up board and safe places to cybermask or retreat to should things go poorly.
Active Turn Role
The Umbra wants to use it's Mimetism and superior stats to engage in firefights against line models. Though they have decent stats in general, going against BS13 models or those with visors is unlikely to work well for them. They also want to move into melee should their opponent's be poor CC fighters or should they have the cover of smoke or cybermask. Umbra are tools designed to kill models and do so well, especially in a link.
When in doubt, dodge. With PH 13 and Kinamatica you can get to safety better than other models. The K1 Umbra will almost always want to use Flash pulse instead of K1 unless the opponent is very close ranged. All umbra are good at the engage skill and want to use it when the can even against other martial artists (they are usual better than them in CC anyway)