LineageOS is the gold standard. The A20s has official or unofficially supported builds for LineageOS 20 (Android 13) and experimental LineageOS 21 (Android 14). It’s minimal, fast, and has excellent battery life. No bloat, no gimmicks. Just pure AOSP with subtle customizations.
Standard Samsung software won't install custom ROMs, so you need a custom recovery like . Samsung A20s Custom Rom
This process will void your warranty and permanently trip the Samsung Knox security bit. LineageOS is the gold standard