Bruther, I've dealt with injuries since 2017/2018. Put some racing together this past year after a year or so off but dug myself into an overtraining hole, and had to take the summer off. I feel great now finally after years of struggling, knock on wood. Hopefully after 12 weeks you'll be able to get back into things, wishing you the best.
If I can offer any advice, it would be:
1) Get outside as much as your injury will allow. I'll say doesn't even matter if it's "doing anything" for your fitness. Go hike. Go open-water swim if you're strong. Hell, go fish. Go do whatever out in the world that you can with your free time. I personally find the structure of training helps me keep my life on track, so I did that -- I picked up road cycling with a tibial stress injury and preserved both a massive chunk of my aerobic strength and my mental health. I also built some muscle mass (which needs to come off now). We as runners love the outdoors and watching nature and people pass and we lose all of that when we get in the pool or in front of a TV while on a machine. Not saying there's a time and place for that, but I'm much more of the thought that injuries can quickly become much more of an emotional and mental battle than a physical one once we take away the human aspects of training for too long.
2) Get strong. Others have said this. Focus on hip strength, core strength, and lower leg strength as well as flexibility and mobility in those areas. I noticed a massive difference just in how my form felt by paying significant attention to these areas. It's made me love running again, when before I was in constant fear of doing damage. I look forward to runs and what the future holds for training.
3) Be smart with your return. Patience is key. You're older than I am, but not old enough to have thrown it all away. Take 6 weeks or so to just walk/jog and feel your feet beneath you again. Build slowly at a comfortable rate after that. Adjust to the mileage level again. Make sure everything feels easy. Once you start formal workouts again, you'll know it was worth it. Trust me.