Those links are from quite a while ago;
For example:
I have voice echo in the Signal app which uses fairphone 3(Feb to Jun 2021)
Echo in VOIP calls - FP3 - #14 by alquimista(Jan - May 2021) RESOLVED
Whatsapp echo on caller side - #4 by Margriet1(Jan to Mar 2021)
That was many updates ago.