Do all supported devices get /e/OS updates with the same frequency?

Do all 269 models get /e/OS updates equally often or does the murena team focus on the 5 models they directly sell?

I’d like to install /e/OS on a shiftphone, but only if I know it’ll get security patches for a while.

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

Supported devices get updates the same way in general.
Exceptions to the rule would be e.g. technical hiccups with building OS updates for a device (can happen temporarily) or having to drop support for a device because development efforts stop being feasible for reasons (e.g. missing LineageOS support going further, /e/OS is based on LineageOS) .

/e/OS on the SHIFT6mq is at Android 11 (R) currently, with the device being on the current (!) list to get Android 12 (S) as well as LineageOS for the device being at Android 12 already, so judging by that updates including security patches should come for a while.