I can offer the following information on this from my own research.

In an effort to generate some probable location information based on the warning signals that I myself work with I have developed some sun and moon location based data processing procedures. They can produce moderately to very good results for some earthquake forecasts. But they are much better at linking warning signals with past earthquakes. And I believe that they are showing that an earthquake can occur within minutes of the expected time.

Those signals can be detected days, weeks, and months before an earthquake. And if solar storms were affecting earthquake occurrence times then it would be difficult to see how they could do that without making it so the signals no longer matched the earthquakes.

That would suggest that the earthquakes would have to be moving from one distinct time slot to another. Or it might indicate that only some of the earthquakes are being affected by the solar storms. The storms could not affect a warning signal generated a month before it occurred.

Here is an additional piece of information which I believe my research is indicating is the case.

Aftershocks are probably regarded as being linked with the original earthquake. And they undoubtedly are. However I will often detect warning signals days and weeks before the original earthquake. Some will match that earthquake. And others will match the aftershocks.

By themselves those types of data would suggest that the original earthquake and the aftershocks have to be completely separate events. But I believe that we know they are linked. And I feel that any general earthquake triggering mechanism which is proposed would probably have to be able to explain those types of data.