Novaliss
I've got multiple accessibility apps installed for various usability improvements, mostly for swiping at the edges of the screen for different shortcuts.
I've tried disabling Developer Options (which made the phone feel sluggish in other ways, because I like keeping Animation speed to 0.5x), but it was worth a shot. Half a day later, I couldn't see an improvement.
Now I've also disabled all accessibility apps to see if it helps. I also cleared data for Launcher and cleared only the cache for SystemUI in all profiles (Owner, Work, Private Space) because the "Clear data" button is grayed out, despite 4.1kB of user data being shown as used. That was 2 hours ago and I can't say it's any better overall.
I tried one last power off/restart and I can confirm what SheeEttin says about the optimization starting once more for (in my case) 11 apps after a fresh start, so that is clearly a sign, especially because it doesn't provide the usual prompt to restart these apps after the optimization process ended.
I can also say with fairly good certainty that the slowness is definitely worse on the Work (i.e. where I have Play Services installed for work/GSuite apps) and on the Private Space profiles. Having the Private Space profile running clearly slows down the phone even more and also makes it warm up a noticeable amount.
If it's useful, maybe I could provide the logs for the GrapheneOS app (i.e. the one that owns the "Optimizing apps" notification)? Where/to who should I send it? Are there any other logs that I can provide? I know it's an issue stemming from a Google update and affecting stock Pixel OS too, so I don't expect you to pour debugging time into a regression that you haven't caused; I'm just offering if anyone's curious enough to take a look.