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Instructions have been moved to https://github.com/francoism90/asus-router. :)
@francoism90 could you please confirm what's the actual Tx power according to those logs
admin@RT-BE88U-B380:/tmp/home/root# wl -i wl0 txpwr_target_max
Maximum Tx Power Target (chanspec:0x1001): 26.00 26.00 26.00 26.00
admin@RT-BE88U-B380:/tmp/home/root# wl -i wl0 txpwr_adj_est
Last adjusted est. power (chanspec:0x1001): 27.50 27.50 27.50 27.50
admin@RT-BE88U-B380:/tmp/home/root# wl -i wl1 txpwr_target_max
Maximum Tx Power Target (chanspec:0x1001): 26.00 26.00 26.00 26.00
admin@RT-BE88U-B380:/tmp/home/root# wl -i wl1 txpwr_adj_est
Last adjusted est. power (chanspec:0xe832): 27.25 27.25 27.50 27.25
admin@RT-BE88U-B380:/tmp/home/root# wl -i wl1 txpwr1
TxPower is 127 qdbm, 31.75 dbm, 1496 mW Override is Off
admin@RT-BE88U-B380:/tmp/home/root# wl -i wl0 txpwr1
TxPower is 127 qdbm, 31.75 dbm, 1496 mW Override is Off