Maybe for others… Read more info about /e/OS: /e/OS - e Foundation - deGoogled unGoogled smartphone operating systems and online services - your data is your data (which is still Android).
You can buy the phone preinstalled from Murena to avoid this.
When Fairphone provided Fairphone Open OS on the Fairphone 2, you had to install it yourself, only the non-lockable bootloader of the Fairphone 2 back then prevented you from having to do the same things as now. So providing something like Fairphone Open OS now wouldn’t help you in this regard.
Most of them should be uninstallable in the way Android provides for preinstalled Apps … Uninstall default apps - #29 by AnotherElk - Setup - /e/OS community
All-time underrated remark regarding custom ROMs on Android phones.
(Keyword AOSP, which all Android OSes, stock as well as custom, are based on)
Or from Iode
So really good options Fairphone is offering with the help of developer of other OSes
Sure there will always be some third party OS which does what you want. In my opinion a privacy friendly OS should be provided and supported by Fairphone directly.
Now that we’ve come such a long way and the hardware is rather fair, let’s make the software fair as well.
In my opinion its good they concentrate on one OS Version and cooperate instead with e/OS or IodeOS, as numbers show that the majority still use and want the easy Google ecosystem and only 5-10% used FPOOS
I also got my FP5 now, willing to help with Google-free development, no matter what OS, anyone spotted some public effort yet?
How easy is it to install an “alternative ROM” and how well do they work without the proprietary binary blobs?
For comparison, the Graphene install on Pixel was so easy I don’t even remember how I did it other than going to their web-page and pressing a button.
I have moved your post as this was off-topic. Else I advice to just use the search funtion in the forum or your search engine of trust.