It seems the new security features inside the M1 will make it extremely difficult to install unsigned apps.
This was known and openly documented by Apple in June. Yes, Apple Silicon Mac require all code to be signed. I disagree that this makes the system more locked-in though. Everything you build on your machine is signed automatically, so open-source stuff etc. is not threatened at all. If you want to distribute, you will have to get a developer account, which is what people already do. So really the only affected devs are those who distribute unsigned apps (which are a security risk anyway).
What I definitely agree with is that Apple should offer free access to signing certificates. Aka. Developer Program lite. No support, no access to preview software, just a certificate linked to a developer identity. This should make things easier for open source developers and the like who might be more adverse to paying $99 for the developer access.