Google has news on what you will need to do for still being able to sideload apps:

* enable developer options
* confirm that you are not tricked
* restart phone and re-authenticate
* wait one day
* confirm with biometrics that you know what you are doing
* decide if you only want unrestricted installs for 1 week or forever
* confirm that you accept the risks
* enjoy the few apps that still have developers motivated to develop for a user-base willing to put up with this

https://goo.gle/advance-flow

@grote 24 hours of not owning my phone is evil. This is stupid. I'm fine with everything but the pointless 24 hour wait and the biometric requirement. Give us your personally identifiable information and wait in phone purgatory for 24 hours to actually be able to own your device? Ridiculous.
@CalcProgrammer1 @grote The 24h waiting sounds the most reasonable part to me...
@itsFriday @grote How so? It's the one that's getting in your way the most. Want to use this app today? Screw you. Why do we cater to idiots getting scammed more than letting people own the devices we bought with our own money?
@CalcProgrammer1 @grote For the scamer scenario, 1 day of patience I see as a workimg precaution. But why do I need to go through hidden steps to get there? Why is there not a question at the very first startup "Would you like to add F-Droid, Aurora, ... and/or the option to install any apk on your phone? Tick the ones you like and it is installed automatically."