Drawing from over 10 years in the IT industry, I have honed my troubleshooting skills, specifically with WordPress installations and configurations. Your issue with the WordPress dashboard being slow on an external IP is within my realm of expertise. I understand your frustration and can promise a focused, diligent effort towards diagnosing and resolving this problem. My proficiency in network troubleshooting will be an asset here.
Additionally, I am familiar with Synology NAS configurations, which could potentially be related to your performance issue. Having faced a similar situation before, I successfully enhanced site performance on an external IP, ensuring a smooth browsing experience for the users.
Lastly, my exposure to the technology stack you're utilizing- LAMP Stack (Linux, Apache, MySQL, PHP), is crucial to utilizing WordPress effectively. With strong command over PHP and Wordpress alongside invaluable experience on Synology NAS configurations, I assure you that together we can address not just the main performance problem but also the secondary one pertaining to theme installation error messages.
Feel free to leverage my skills in your business and set a course for success! You can count on me to provide not only swift solutions but also regular communication and complete transparency throughout the process. Let's get started!
Best,
DK