How to register an old, out of state vehicle that belonged to a deceased person?

This is kind of a long story, so bare with me.

I have a 1991 Jeep Grand Cherokee that belonged to my dad, but was *registered* to my (common law) step-mother. They lived in California and both passed away suddenly in 2015. The vehicle registration expired that same year, *after* I'd already moved to Minnesota, in the vehicle. At the time, I figured I'd register it once I got where I was going. I know this was a stupid move, now, but back then I'd just lost two family members and wanted away from that state as fast as possible. Hindsight is 20/20, as they say.

I tried to register it when I moved here, and for a lot of reasons to do with miscommunication and paperwork I was unable to get from my step-brother (who I no longer have contact with after he gifted me the vehicle), I was unable to do so. The Minnesota DMV basically just shrugged and said, "nothing we can do."

So this vehicle has just been sitting in my garage at the apartments where I live, with out-of-state plates and expired tabs for years. After some testing, I think it will still run if I drain and replace the fuel, but the tires are flat now and it technically won't start without intervention and minor repairs.

Cut to now, when we've just bought a house and need to move it out of that garage. I've wanted to register it since 2015, but just assumed that I'm stuck with this vehicle and can't do anything with it because of what the DMV said all those years ago.

A friend recommended I try to register it as an abandoned vehicle, but I don't know what I need to do for that, and looking at the Minnesota DMV website really just made me more confused. Can someone explain, like I'm stupid, what information exactly I need to gather before trying to register this Jeep again? I really don't want them to just say there is nothing they can do like last time because I mess up this process somehow.

Any advice at all is welcome.

TL;DR: Moved a vehicle registered to my deceased step-mom from CA to MN in 2015 and then tried to register it. Couldn't due to multiple reasons, now it's been sitting there for years with expired out-of-state plates and I want to try and register it again. Advice?

(also posted in r/NoStupidQuestions)