Every time I log into Fedi, I see another post with a guide called something like "Activist's Guide to Smartphones" or "Phone Security Guide for Protesters," and every single one of these assumes that the threat model is the kind of police force that exists under liberal democracy where the law will afford significant protections to protesters. The world is changing, and these guides not only fail to address the threat of an actively hostile fascistic anti-democratic occupying force (I refer here to the police), but such guides generally are limited to "what" and "how" but miss the more critical "why."
If you believe that you are facing fascism (or even something close to it), can I please please please convince you to read something written by anarchists who have faced serious repression and are trying to convey just how much phones can lead to the imprisonment of you and your friends for even things that are allegedly "legal."
https://opsec.riotmedicine.net/downloads#mobile-phone-security
Overwhelmingly these guides seem to come from InfoSec or civil liberties focused individuals, groups, or NGOs, but bloody hell, the danger they face tends to pale in comparison to what radicals face, and the level of concern they have is likely far lower than it should be. Watching across the pond at this advice circulating, all I can think is that such liberal notions of rights are security are going to get activists killed or imprisoned for life.
(not that my advice is perfect. always get a second source. compare what we/i have written to these liberal guides, and diligently study where and how they diverge.)