You could put your "channel" to "auto" and the "channels" to a very specific, hand crafted list of wifi channels.
See: https://openwrt.org/docs/guide-user/network/wifi/basic#common_options
That will not cause your router to constantly look for new channels to hop to, but it will at least make channel auto-detection only consider this specific list.
If I'm not mistaken, the range from 5470MHz to 5725MHz should mp to channels 96 to 144. That's what the FR regulatory domain allows with enabled DFS at 500mW.
But as far as I know, detecting radar on a DFS channel requires this channel to be freed for at least a couple of minutes. So if radar is detected, that channel is marked as unusable for the foreseeable future and another channel gets used. That might repeat a couple of times, until either your router finds a channel that is not in conflict with radar, or until there is no channel left (that wasn't marked as unusable before).
So there are three possible scenarios here:
- Your router might just try another DFS channel and keeps hopping all the time. That's when "cooldown" for conflicting channels hits earlier than radar conflicts happen.
- Your router might finally settle on one of the channels, if your area has at least one DFS channel not in use for radar.
- Your router might turn off 5GHz entirely. That's when all DFS channels are used for radar and there is no DFS channel free at all.
But of course using 80MHz channels will make DFS triggers 4 times more likely than 20MHz channels because a 80MHz channel is completely unusable as soon as one of its 20MHz slices is unusable. So you might be better off using 40MHz channels, or maybe even 20MHz channels.