>

I am unsure of the veracity of that persons claim... 
However, Nalvany is less anti-Ukraine invasion and more anti-Putin. He still has strong nationalistic views, was pro-Crimean annexation, has stated if he became president, he wouldn't return Crimea, has made statements before with the same lines as Putin that Russia deserves a say in the domestic affairs of ex-soviet nations.
The only upside of him would be his anti-corruption stance. Which would be great for the average Russian... but could you imagine if there wasn't the widespread corruption like their is? Id the money that was supposed to be spent on the military was actually spent on military... not that Nalvany would have necessarily invaded Ukraine.. but the whole anti corruption stance mixed with the whole "Russia deserves a say in the domestic affairs of ex soviet nations" stance leads me to believe he would still use military pressure to get what he wants.
I'm honestly amazed Putin hasn't just had this guy killed. He's killed so many other opposers to his regime.
Is he scared Navalny would become a martyr? Or is having him in prison like a trophy or something? >

If Navalny dies, his supporters will find a new leader of their cause, and become less manageable. As long as he lives, his supporters will never agree on a replacement. >

True, but there are Pro-Navalny Russians that have since gone full Z. >

Not sure this is true. Didn't find any such people online or elsewhere.
Being Z means mostly fully trust the state propaganda, and this prevents being pro-navalny.