Current iodeOS (Android 15) on a Shiftphone 6mq
The speaker is not loud enough for e.g. listening to music or for video streaming. Max volume is still too low.
This was even worse with /e/OS Android 13 and on early stock ROM for this phone.
Volume was not overwhelming but okay with later stock ROM and it is less bad with LineageOS forks with Android 15 than it was with Android 13.
This means this issue can be fixed by ROM developers.