Would not recommend installing OpenWrt on any routers with the MT7621/MT7615N combination, due to known 5 GHz Wifi problem.
e.g. DIR-878, DIR-882, DIR-2640...
Not uncommon for devices connecting to above routers via 5 GHz WiFi to display the following error:
Connected, no internet.
Connection to the router is fine/excellent but trying to open a webpage resulting the following error:
Address Not Found
According to lukasz92:
This problem is as old as mt76 driver; will not be fixed.
Problem was definitely present in all the recent 22.03.0 RC releases, except RC6?
Problem is definitely still present in the Stable 21.02.3, 21.02.5 releases.
For those who do not have time/interest going through this entire thread,
The release - *now deleted by arinc9 appears to avoid the 5 GHz WiFi problems and increases routing performance.
EDIT: With the removal of arinc9 releases, Snapshots appear to have least amount of problems.
Note: As of August 21, 2022, hauke has applied arinc9's patch into master = Snapshots as of that date should include the patch.
With that said,
arinc9 deleted the mt7621-dts-work branch August 24, 2022.
The current 22.03.x stable releases do not include all of arinc9's patches.
A quick summary as of September 2022,
For those who prefer stable releases
The 22.03.3 Stable release appears to have least amount of problems as of January 2023. But, expect a loss in routing performance since it does not include arinc9's patches.
Update: As of May 28, 2023: Snapshots work but 5 GHz still slower than 2.4 GHz in performance.
e.g. Sample web page which took 8 seconds to load completely with 2.4GHz, required 30 seconds for same web page using 5 GHz. With that said, it is a vast improvement over the previous times, which were approximately a minute or longer on the 5 GHz WiFi.