I just can't see why Putin would have him killed. It makes no sense to me, he was already in prison, why make him a martyr now, before elections? As an idea elections in Russia are this month.
We also know Tucker interviewed him shortly before Navalny died and we know that Navalny chose to be in Russia. Maybe CIA wanted to not allow people to process the interview and move to martyr Navalny. There are some spicy stuff in the interview like the US blowing Northstream pipeline and Nazis in Ukraine so who knows.
Every media and politician is 100% sure Putin killed him without even considering any alternative.
My take is that the CIA killed Navalny in order to start unrest before elections or to make sure normies keep funding Ukraine.
Someone once pointed out that all these 'killings' have some sort of connection to the UK. Which is interesting. I certainly wouldn't put it past a country that hands over 11- year-old girls to Muslim rape gangs, ignores it for decades and protects rapists, to kill people in order to try to pin it on Russia. (That said, they did not have much of a motive before 2022, as London was a hub for Russian oligarchs and corruption.)
As far as the killings are concerned, it seems that none of them have any proven connection with Putin beyond the convenient assumptions of brainwashed Western audiences. The recent biography of Putin by Short makes short shrift of such audiences - including the 'probably false flag terrorist attack' that you mention. Russia is a corrupt country full of mafia types, and there are a lot of people who want to be rid of certain people, far beyond the Western inclination to blame everything that they don't like on the Bad Russian Man.
If the UK had launched into a war with russia after any of these killings, you might have something. But they didn't. They didn't really capitalize on any of them. It's just not plausible to kill so many people over decades to "pin it on russia" without ever doing the pinning. At this point they'd just be working for russia.
Also the sheer number of conspirators you'd need for polonium, novochok, bombs, gunmen, heart attack laser satellites or whatever you think killed Navalny, this would need official sanction by higher ups.
Though one corollary of that is to effectively run such a place, you need to be seen by those types as the meanest bastard in the room. Even where he doesn't have someone killed he probably wants people imagining he did have that person killed, but with plausible deniability for everyone else.