Usually, /e/OS builds are based on LineageOS builds, and there is not a build for the Pixel 9a yet, see Devices | LineageOS Wiki There will probably not be a build for the Pixel 9a in the coming weeks
(There are some exceptions to this rule like e.g. the Fairphone 6, but I would not assume that this is the case for the Pixel 9a.)
Just my 2 cents: GrapheneOS is an excellent choice IMHO (strange discussions between them and /e/OS notwithstanding - I am reminded of the feuds between the anti-roman groups in “Life of Brian”…). If you are looking for a ROM that uses microG and supports the Pixel 9a, you may consider Install CalyxOS. (Please note that the ROM releases are paused at the moment, but will resume in two or three months.)
{grin} I had Calyxos on it but removed it. Calyx seems to be in a bit of a crossroads moment. No updates for quite some period as they change internal structures.
After 3 weeks I beg to differ. I believe it has been excellent but I am running into problem after problem. With calyxos gone for a while there is nothing to choose from. Looks like I need to buy a new 5G phone that /e/os has a build for.
Bummer as I really like the size and feel of the 9a.
Can you maybe share what kind of problems you are referring to? I am thinking of installing GrapheneOS (while I’m waiting for LineageOS / /e/os) on Pixel 9a myself…