Hi and good evening @quadratum-braccas, welcome to the /e/ community forum. Thanks for your interest in eOS.
Smartphones are usually closely tight together from their hardware and software side. Development from hard- and software goes hand in hand. That’s why unfortunately it is not that easy to make a third partly operating system (such as /e/) for a new phone, as there are many adaptations needed and all the sources of the original software are not available in order to facilitate this adaptation process.
This adaptation process is pretty costly in money or in time.
That’s why you don’t find a lot of recent phones with third party systems such as /e/ out there.
There are software developers passionate about developing third party and open source operating systems for smartphones - especially for popular ones. But it always takes time. For now, you find LineageOS (a third party operating system that serves as well as foundation for /e/) available for the Galaxy S10 and probably soon for the S20 as well. The S21 might take quite some months until a stable version will be available. Once LineageOS is available for a phone model, it is easy to run /e/ on the same device.
If you are interested in /e/ it would be probably more advisable to check first on what devices it is currently running - before you purchase one.
For now, /e/ can be installed on more than 150 devices. Some few (refurbished and new ones) can be purchased with /e/ preinstalled.
I am afraid, that’s the reason why you will probably not find someone stepping up to ‘just’ support the phones you propose.
I am afraid, I don’t have a ‘better’ answer for you for now.
With best regards.