I see another setting has been changed – alternate-sample-rate = 96000
you might want to try resample-method=speex-float-5 for resampling to a higher bitrate
or resample-method=soxr-hq – soxr resampler can offer better quality but might add latency to the audio stream
But you will only likely to hear any difference on headphones
Pulseaudio and Pipewire are both shown in inxi data as running: yes , so the suggested commands were not effective for stopping Pipewire (but stopping Pipewire would not affect audio quality)
I found a picture of the internal speakers and a benchmark of the audio response
https://www.notebookcheck.net/Lenovo-ThinkPad-T490s-i5-Low-Power-FHD-Laptop-Review.420689.0.html
The focus of the speakers is the clear production of high tones, so the device is mainly suited for calls/conferences. This is obviously not a bad thing for an office laptop, but you quickly want better speakers when you watch a video or listen to music. We recommend headphones or external speakers for better quality.not very loud speakers (70.2 dB)
nearly no bass - on average 19.1% lower than median
73% of all tested devices in this class were better
These micro speakers are not good for music even with all the proprietary OS tweaks
You might want to try out AUR packages Viper4Linux or JamesDSP4Linux instead of just an equalizer. Or easyeffects if you replace PulseAudio with Pipewire