How are they going to handle the differences in the ships?

The Nostromo is a f... old mining ship.

The Prometheus was a top quality private ship owned by Weyland.

Anything can be explained...

Well...  I think Ridley will ignore it.  He wanted to do giant transparent displays back in the day, but the tech wasn't there.  He (or anyone else) will argue that the Nostromo crew were just space truckers.  Hauling a load, nothing more.  So simple tech etc.

Honestly, if he cared about continuity he would have used the same type of displays etc in Prometheus.  I think Ridley will not attempt to really explain it.

Star Wars did the same thing.  Episode I and II had some crazy tech.  Then suddenly Episode III ends with simple panels etc.

I honestly do not have a problem with it.  Prometheus, Covenant, etc can all be super advanced.  I am fine with the truckers having the cheap ship.  ALIEN is in a class all by itself.  A PERFECT movie.

Honestly, I still can get a futuristic vibe from the Nostromo. In Covenant the monitors are just regular tvs from Best Buy. Syd Mead conceptual work is sorely missed.

If the Covenant was on a one-way mission originally, the tech had to last the mission.   With the Nostromo, there might be multiple missions - yeah, simple is better - none of those Best Buy monitors!

I think that after we have done the alien prequel trilogy, which is what Ridley promised prior Prometheus. I think he is aiming at doing Alien again.

I beg to differ regarding the aesthetic appeal of the Nostromo, as I find it superior to the clean and sober design of the luxury line....err I mean exploration ship Prometheus and the slightly darker colony ship Covenant. Speaking of the Covenant, the exterior hull of that ship looked like something from the same era as the Nostromo, especially when its antennas were extended.

The Nostromo looks dirty, oily and realistic as an old towing ship, and the old tech aboard that ship still works for me, in part because it isn't supposed to be fancy for a bunch of underpaid miners, but also considering how well it worked in Alien Isolation that is very much based on the same design of the first film in most aspects. 

Unless no old mining ship shows up in the sequels, I'm fine with Ridley continuing with the use of advanced technology such as holographic displays etc instead of 70's computers (that sort of look retrofuturistic anyway) 

Covenant starship was just [retro style] and Nostromo’s starship drifting through space some [ghotic, retro style] in my opinion with older technology systems than Covenant ship worth taking a look at inside narrow and overwhelming, especially the angar section is amazing.

lets look at the ships so far.

The Nostromo- A mining vessel. not designed in any way to be comfortable, its a truck in space. remember. mines on earth now are not aesthetically pleasing they are dirty, basic and get the job done.

The Prometheus- when i first saw the prometheus i was not to happy with how advanced it was considering it is set before Alien. But then we have to remember this is the equivalent of a luxury liner owned by the richest man, and the richest company in existence. interestingly though it did lack MuThEr.

Covenant - more advanced then the Nostromo, but far less then Prometheus. Fair enough its a colony ship with one of the first colonists expeditions, its going to be more advanced and design for such a long haul. I didn't like MuThEr being so talkative i must admit, to much star trek for me. 

Sulaco - OK so this is not R Scotts, so it may not count but as a Marine Vessell you would of expected its o be far more advanced then it was. If any vessel is out of place its this one.