Ok, I uploaded this question on General Discussion, but I got an advice to upload it on Story, Art & Sound, so I re-upload the same question here.
Since Noxus is expansionist, probably it wants to expand its territory. However, both Freljord and Shurima are harsh places. One is extremely cold and the other is a desert. Will Noxus be interested in those regions? (Or was Noxus interested in those regions?)
What do you think?
They ARE invading both.
In fact, Noxians already conquered parts of Shurima.
A number of ports and cities in northern Shurima were voluntarily assimilated into the empire. The original inhabitants of these settlements live in relative peace with their Noxian counterparts, seeing the exchange of food and preferential trade as a price worth paying for military protection from raiders.
https://leagueoflegends.fandom.com/wiki/Bel%27zhun
And Darius himself has led the fight in the Freljord (his son died there, but he didnt knew that it was his son)
The incursions in Shurima happened long ago and didnt seem to get any continuation since. And going by Cassioepeia bio were likely guided by the BR, who had Darkwill as their puppet at the time.
However, Darius stopped the Freljord campaign just because he didnt have the tropps and supplies to keep fighting, he didnt continue the campaign when he returned because of his new place in the Trifarix and so he could realocate the troops. However we have seen in his color story that he has returned to the Freljord recently, looking to reclaim territory lot during the first campaign. So yeah the invasion in Freljord is still going on while the Shuriman one seems to have stopped long ago.
However with the news about Azir rise, which started to spread around the same time when Swain estabilished the Trifarix, there's probally noxian plans for Shurima, or at least they will have a careful eye upon it. But I dont think they're going for an actual invasion for now, at least not while they dont have a chance to do something revelant, which is kinda hard on the current Azir vs Xerath layout.
Also, we have actually seen other instances of Freljordians fighting Noxians since the estabilishment of the Trifarix while the same cant be said about Shurima:
Ashe cheered with the others when the Red Snows recounted the defeat of the Noxian warbands that had tried to advance inland from the coast.
The Harder Way - Ashe color story
They were able to fend off other raiding tribes, slay the great beasts of the mountains, and repel Noxians encroaching to the south.
Tryndamere bio(this one can be argued to be during the first invasion but still)
Now, as the seasons turn, Sejuani marches on the southern tribes, Noxian interlopers...
Sejuani bio
And Daruis color story as I mentioned before.
Dude. Visit the Universe site, you'll find everything you want right there. Rather than someone else divulge it for ya.
I don't understand why Noxus did not take the chance to attack and heavily damage Demacia with Sylas having created a war inside the walls of Demacia. Noxus has spies in Demacia (and I believe the Black Rose killed J3 but that is just me) and since they probably knew what was going on, couldn't they form an army and attack them? Plot hole here
The funny thing to me about Noxus is they are so arrogant that they'd attack anything in order to expand (as mentioned by other comments they already started with Freljord and Shurima) but don't exactly know what they're messing with that's out of their league.
Hell, they might even have the nerves to try to conquer the Void or even the Shadow Isles.
