Our ISP doubled our speed from 125 to 250Mbps. No issues when connecting via LAN cable. My issue is when connecting to SSID 1(5GHZ) speed I obtained are only 100Mbps. Anyone can help me with this issue?
Is there a particular reason you are running such an old version of OpenWrt and looking for support? Why not do a clean install to 22.03 and try again. I get way over 200Mb on Wi-Fi with my wrt32x which is similar hardware.
Off the bat, I would recommend upgrading. 19.07 has reached EOL some time ago, and there are numerous security issues that you should address.
Beyond that, nothing has changed from 19.07 on the wireless front on these devices (probably why there has been little response). It has been long abandoned.
FWIW, I gave up and just point my wireless IOT devices at the Linksys 2.4, but run everything else through a dedicated AP.
Glad to hear that. Since you have the WRT1900 (which has the 88W8864 wifi chip), you may want to add this fix to reduce wifi latency spikes specific to that chip: