This is a variant of StallordD's Goat God build. His original youtube video is here. Needs one less Forma if you use normal [Intensify], and realistically speaking it probably won't get you killed in any situation where [Umbral Intensify] would've saved you, but who can say, really?

Cast Empower, proc [Growing Power], proc [Energy Conversion], then cast Renewal. Then, cast Hallowed Ground at least once and walk over it to get the Iron Renewel buff. If you're playing high-level, consider casting Renewal sooner to keep yourself alive and re-cast when you have the procs ready to go. Watch out for Nullification fields from Corpus bubble bois and other assorted sources. The build's biggest Achilles Heel is Infested, since there's no way to [Protect] yourself from losing energy to the Ancient [Disruptor]'s buff, and a horde buffed by one ruins the entire feedback loop. Watch for the visual effect on nearby infested and prioritize every Ancient you can see when you catch it. If you get shut down, you'll have to re-cast Empower, re-proc the conditionals and re-cast Renewal, plus cast Hallowed Ground again to regain the Iron Renewal buff. Note that your Renewal cast is also lost if you fall into a pit or go through host migration, also requiring everything to be re-proc'd. If you've avoided these problems, remember to re-proc and re-cast Renewal later on as Molt Augmented gains stacks.

StallordD recommends throwing on Decaying Dragon Key to lower your shields and thus proc Rage/[Hunter Adrenaline] more often. It seems unnecessary at higher levels considering how fast enemies can take down your shield anyway, but YMMV. It's better for team play where you may be shot less reliably, especially if your entire team has brought heavy crowd control. Also, remember to take it off when you switch frames.

Dispensary is a good alternative to Empower for the Helminth ability; you lose some HPS but you worry less about running out of energy. With energy as less of a worry you can swap Flow or Continuity out for Adaptation (an unranked Adaptation won't require re-polarizing the slot.) Honestly, [Adaptation] is probably a better choice than [Continuity] when you're solo'ing anyway.

There are a couple alternate choices for Arcanes: [Guardian] for more damage mitigation, or Energize to help keep your energy from running out. Energize is a great choice for group play to compensate for getting less energy off of Rage/[Hunter Adrenaline]. Nullifier is a great choice for avoiding sneaky Magnetic procs that will shut down your heals. It will stop Eximus leeches, but alas, it doesn't stop Ancient Disruptors; if only it were that easy.

An unfortunate downside of turning the goat into a tank is that, without buffed range, you can't blanket huge swaths of areas in Hallowed Ground, and you also have to cast it more sparingly instead of spamming it constantly, lest you run down your energy before enemies can shoot you. It's still worth keeping a finger on 2 for it, though, because both the debuff cleanse and hitting crowds of enemies with Radiation procs are always valuable.

If you're healing a team as well as yourself, glance at their names on your HUD every now and then to make sure they haven't lost Renewal, and cast Hallowed Ground where they'll walk over it to get Iron Renewal. Also, your teammates in Arbitration may be annoyed that you don't have [Phoenix Renewal] to rez them when they die like casuals, but they'll get over it. If your intent is to support the team as much as possible, however, and not just heal them as a bonus while you tank, just switch off Oberon entirely; Renewal is super-finicky to keep going on other players so other frames are less aggravating as support. Allies do not have to remain in your ability range to keep Renewal, but they will also lose it if they fall down a hole, and they can't re-gain it by walking back into your ability range, you have to actually re-cast it to give it to them again. If you really want to use [Oberon] as actual support, just a use a more standard build with range for Hallowed Ground with less healing but without the conditionals that all need to be proc'd, so you can easily re-cast to give your squaddies the Renewal effect back.

While it's not completely invincible and lacks common support abilities, it's enough of a tank to work well for nonsense like Eidolons or Orb Mothers, to say nothing of high-level/SP endless modes. Throw on a weapon with good AOE like a [Kuva Bramma] or and you've got EZ mode for Arbitration and an easier time catching the enemies that can shut you down. Steel Path needs a good weapon built for it anyway since the frame is focused entirely on tanking and occasionally inflicting radiation procs.