This is sort of my problem.
In this scenario the sentinel has 2km of penetration with it's sight past the line of contact. Easily enough to get significant vision on a lot of your assets for strikes and predict any advances coming.

The enemy long range air defence just has to be within 3.5km of the front to cover that, and is out of range of most artillery. Your heavy artillery would need to get into range of their short range assets such as light arty, helicopters etc to strike it.
Presuming you have koalit/smerch, if you don't get fucked.

Your AD needs radar on and to be within 2.5km of the front to see the sentinel. Dangerous vs HARM spam, but you can get away with having radar on a lot if you use ZSU to distract SEAD. At risk of being hit by enemy battery though.
Iron Thunder just need to get within 2.5km of the LoC, safe from your short range assets, to counter you. PrSM only 5.5km, GMLRS 4km.

Often in my experience the enemy AD will have a launcher positioned even closer, but is unlikely to have radar on. RU is generally lacking in SEAD as effecient as prowlers, but you're likely to fly into PIVADs/SHORADs if you do. Its not unresonable for the opponent to keep at least 1 radar on a patriot to cover the sentinel.

And this isn't even touching on that your plane can only see the sentinel at the closest point of their circles, 99% of the time they won't line up like that, you'd want to see a bit of the sentinel's circle from a significant part of yours, which requires you to be even closer.
If the enemy is aware of what you're trying to do advancing a heavy AD forward and flicking it's RADAR on every now and again to scan for you is more than enough to shut down the entire strat. Or noticing your idling plane with any of their planes that come in for strikes.
If you loitered a stealth plane it'd work better, but then you're expending an SU-57 for this and his stealth sucks.