I've got 2 s21 at home. Both with 1-2 bars while I had max on my s8. Speedtest has gone down as well. I've never had under 10mb/s before. Normally 40 to 70mb/s on s8. Its a joke now.
Also I use Internet radio on my regular route in my car. Signal was dropping at 1 place on s8. Now my Internet radio is basically unusable.
I don't know it this will work for you, but for me it did the trick:
In the APN settings, enter the Bearer option and uncheck everything, check check only LTE.
Save, reboot and check.
It upped my bars from 1 to 3 on 4G Orange România.
Let me know if it did any change with your reception.