73ʞk13

The original overview dates back to 2023 but is updated, e.g. to mention EoL of DivestOS. Security updates are observed over a longer period of time. Its criticism is that though updates are provided monthly their release in comparision to the release of the patches is delayed by some days and sometimes incomplete. Can be compared here: https://source.android.com/docs/security/bulletin/asb-overview and here: https://calyxos.org/news/ The original overview in German can be found here: https://www.kuketz-blog.de/android-grapheneos-calyxos-und-co-unter-der-lupe-custom-roms-teil1/

I’d recommend iodéOS instead of /e/OS as the former is considered a bit more secure than the latter, see overview of Custom ROMs here (summarized from a well known German IT-Security Blog). You can also buy a FP5 with iodé preinstalled.

I have an Asus Eee PC from 2009 running Puppy Linux (as a secondary device).
As already pointed out you will need a leightweight distro and desktop environment.

https://distrochooser.de/ (available in English) can help you find the right distro, it takes into account the age of your device, your Linux knowledge, use case and a lot more.