The flu has largely disappeared; even with higher than normal testing, the numbers of lab confirmed flu have fallen to historic lows. https://twitter.com/kerpen/status/1352651926626832384

This trend has been observed worldwide with masks and lockdowns receiving credit in the media. But, that theory implies that NPIs are nearly perfectly effective against the flu but completely ineffective against Covid. https://www.wsj.com/articles/covid-19-has-nearly-wiped-out-the-fluhow-do-we-keep-it-from-coming-back-11611230410?mod=hp_lead_pos6

A more likely cause of the historically mild flu season is viral interference: essentially, Covid has crowded out the flu this year.

This pattern was observed in 2009 with the h1n1 pandemic, when the new flu strain eliminated essentially all other respiratory infections:

In 2009, h1n1 accounted for 94% of flu cases. Interestingly, that pandemic also had a Spring/Fall pattern (like Covid). Winter seasonal infections started earlier than normal and ended earlier than normal. Importantly, after h1n1 ended in Jan, other viruses remained low.

The following year (2010), Winter seasonal respiratory infections returned to their normal pattern:

Based upon the experience with h1n1, the most likely outcome is that viral infections will remain suppressed this Winter even as Covid infections wane. Next year, however, we should expect the flu to return to normal transmission patterns.