Read someone on the mains claim that he was in discomfort from a long flight. If this current plan doesn't work then in my dream world they would throw caution to the wind and take the time to work his deadlift up to 500+ lbs. His frame isn't properly fortified, but certainly could be if they prioritized it. A few NBA superstars are on this already. Steph Curry (former injury issues turned mostly healthy at highest level) deadlifted 400+ years ago and has only gotten stronger since. Strength is key to staying healthy.
Rehab aside I think he generally needs to become far sturdier in order to even play his game at the NHL level. He's critiqued for just physically dominating at the junior level, which often doesn't translate to the NHL. However he has the frame and athleticism to physically dominate the NHL as well, as long as he fills that huge frame out. My stance is he's too skinny to play how he is inclined to and that's been his problem from the start. He could play physically dominating hockey in the NHL if he was muscular enough.
Disclaimer - the rest of this post will be me talking out of my ass, due to the fact I don't know exactly how Lindstrom's pain is presenting, and what they have already tried. I'm just a guy that lifts weights and all I really have to go off of are my personal anecdotes. I haven't formally studied any of this stuff, but low back pain wise I went from consistent and painful problems (struggled to get in and out of chairs, couldn't bend over without sharp tightness) at ages 18-20ish to a 625 conventional deadlift and a 405 lbs zercher deadlift at age 23, all with a pain free back. I am not an athlete with lots of money invested in to me, so I am free to take risks and say "screw it, my back hurts anyway why not just try to lift my way out of it" with far less to lose than Lindstrom. For me it has worked. I feel very blessed to be at this point, but I don't believe it was pure luck either. Lastly I know Lindstrom's issue may be entirely different than what mine was. I don't even know what mine was anyway, I just had very bad back pain at the exact same age he's experiencing it, and after thousands of reps I can lift 405 lbs off of the ground with my elbows under the bar. Also the lift variations I will mention all pop up on Google, they're obscure but gaining popularity.
If I were put in charge of his rehab he would be doing light jefferson curls, working up to 135+ lbs for reps over time. If he can't perform those then he can't play hockey IMO. After some basic spinal erector strength and function/capability is built up then he could do some deadlift variations that feel easy on the back but build strength in "awkward"/asymmetrical positions like jefferson deadlifts (different that aforementioned J Curls), one handed deadlifts all for injury prevention, with some classic RDLs for some size and regular/trap bar deadlifts for size and explosion. All of which can be scaled properly with regard to pain, and can be safely progressed pain free. I'm talking start very light and build up very slowly.
I don't know the exact mechanisms of which disc of his was herniated, but I've seen studies claim around 35% of the population has disc herniations to some extent, obviously most of which are asymptomatic. Experiencing what I've felt in my low back I suspect I'm part of that 35%, but I've never been diagnosed so I cannot say for sure. My only firm claim I'll make in this post is that I reject the idea that it's dangerous to train the spine in a rounded or bended manner. Keeping it rigid during exercises doesn't apply to the real world. We have to bend over, twist, and move the spine in a huge range of motion throughout life (hockey players especially!!) and from what I have seen/experienced there are tremendous benefits to safely training the spine and it's supportive musculature to do all of those things.