As an accomplished Apache Server Administrator, I possess a vast array of experience in managing and troubleshooting servers, extensively with Apache and MySQL. What sets me apart is my deep expertise with CentOS, AlmaLinux (which is the exact OS of your servers) and my understanding of user permissions and authentication methods within MySQL. Over the course of 11 years, I have overseen the setup from scratch, optimization, and management of numerous dedicated/shared and VPSs across various control panels such as cPanel, Directadmin, CWP, Plesk, and VestaCP.
In line with your project needs, I have successfully established remote MySQL connections between servers over multiple cloud platforms like GoDaddy including AWS, GCP and Azure. My experience includes configuring load balancers, implementing backup strategies and resolving a diverse range of errors like the 'Connection failed: SQLSTATE[HY000] [1045]' that you mentioned.
Additionally, my valuable experience as a Cloud Engineer offers a unique perspective to ensure the best outcome for your project. I've done similar tasks involving RDS MySQL upgrade without disruptions.I'm confident that my skills and experiences will effectively aid in reestablishing your remote MySQL connection. Don't hesitate to let me know if you need any clarifications or additional information!