What 2 princes and love triangle?
While there's some similar situation, in term of actual feelings, pretty much all of them have a least one person doing it for political reason only so I don't want to count that as love triangle.
Like, even with the 2 princes from royal family and the princess from the #1 domain, only one of the two prince was in love with her (the only reason he even competed with his brother)
Though thanks to Myne getting involved with the latter and the princess, she ends up help the two get together (the tl;dr is that both of them give up their rights to the throne)
That said, Myne's long range blessing for the two ended up causing more chaos in the end...so yeah.
Although I said that Myne and Ferdinand's reason for getting engaged isn't exactly due to romantic passion, the way they act kinda fit how the society expect 2 people in love to act (given Ferdinand's personality, his actions are likely intentional)
For example, in order for 2 betrothed to get used to each other's magic power, they often gift each other with a magic tool filled with their own magic power.
Well, Ferdinand pretty much always have Myne covered in all kind of defense accessories, both to help her drain her excess mana and to keep her safe.
But for people who don't know much, he's the exact image of a man protecting his waifu.
Myne on the other hand, had once described Ferdinand as THE perfect husband for her if she's ever getting married (although one large reason was him giving his library to her when he left the domain)
And during their reunion, Lutz's POV chapter noted how Myne acted exactly like a maiden in love when she denied she's in love with Ferdinand (blushing furiously, which is the first time Lutz has ever seen such reaction from her and gave his approval for Ferd for that)
Also if you read the other spoilers above:
When Ferdinand did his memory diving thing, he dyed Myne in his color.
So in term of how magically compatible they are, these two are 'perfect match'
(While he's a schemer, based on a few other things I do not think he intentionally dyed her)
But just to give you an idea:
Obviously since Myne got engaged before, she got the engagement magic tools from her previous partners.
Well, the first one was her adoptive brother, but both knew it was just for political reason (avoid civil war since Myne is way more qualified for the seat, but she's adopted) so they never did this, and any item that might be seen as for that purpose actually came from Ferdinand, including this hairpin that used a rainbow magic stone (very rare and valuable)
Then later on when the royal prince got engaged to Myne in order to secure the key for running the country-running magic tool that Myne had, he gave her one.
Except at one point another noble pointed out that the tool was turning into dust, due to magic power overload, and angrily commented how unfit the prince is to be her partner if his magic tool can't even handle his partner's magic power (since magic power level difference is part of judging whether two people's magic is compatible, thus why there's very little, if any, marriage between people of different social level because those are judged based on magic power level)