Navalny has always been a supporter of a concept referred to as "Russkiy Mir"[1] and has spoke at length about it. It is a weird ethno religious philosophy which shows the bounds of the russian country extend far past the borders of teh russian federation. The closest I can easily describe it is as a weird western version of jihad where they want to assume all other cultures and erase them in favor of expansion of their own via multiple methods.
In 2007, in a Russian "Gun Rights" video, Navalny compared the Chechen muslims to "cockroaches and flies" and said he wanted to exterminate them. A picture of a Chechen muslim appears on the screen and he shoots it with a pistol. In another [2] video it featured Navalny dressed as a dentist, presenting a slightly confusing parable that likened interethnic conflict in Russia to cavities and argued that fascism can be prevented only by deporting migrants from Russia. Navalny closed his monologue with “We have a right to be [ethnic] Russians in Russia. And we will defend this right.” This is an allegory to killing all non-ethnic Russians.
In 2008 when Russia invaded the country of Georgia. He said[3]:
Of course, there is a big desire to fire a cruise missile at the General Staff of the [derogative name for Georgians], but they are just waiting for this.
Years later, he apologized for the ethnic slur denoting Georgian people, but never for his support of the Russian war on Georgia.
In an interview with Echo of Moscow radio station in October 2014, Navalny admitted that the peninsula had been seized through “outrageous violations of all international norms”, and yet asserted that it would “remain part of Russia” and would “never become part of Ukraine in the foreseeable future”.
His statement was not simply an assessment of the developments around Crimea. When pressed on whether he would return Crimea to Ukraine were he to become Russia’s president, Navalny wrapped his “No” in an odd question: “What? Is Crimea a sandwich or something that you can take and give back?” His position on Crimea was basically, "finders keepers."
Also in 2014, here[4] he is using one of the worst ethnic slurs for Ukrainians making fun of them.
In 2016, Navalny said that he intended to hold a "normal" referendum in Russian-occupied Crimea if he won the Russian presidential election. Note that Russia has forcibly killed or deported many/most ethnic Tatar peoples and native Ukrainians from Crimea. They've allowed Russian people to come occupy it and settle the lands, so by definition, any referendum would be with invaders on invaded territory. It would be a sham.
In 2023, he offered a 15 point "manifesto"[5] where he changed tac quite a bit, but this was after some prominent navalnyists were pissing off western journalists with their staunch anti-ukraine message, all in line with Russkiy Mir.
I can go on and on and on, but his support of violence and cleansing the world of non-russians goes back a long time. I just spent a few minutes to find these but if you dig in you can find the same and more.
[1] https://dgap.org/en/events/russkiy-mir-russian-world
[2] https://www.youtube.com/watch?v=ICoc2VmGdfw
[3] https://navalny.livejournal.com/274456.html
[4] https://twitter.com/navalny/status/505215151961014272
[5] https://twitter.com/navalny/status/1627632098608644099