or a high quality stock fund
...
I'm not sure if such a thing exists. Precious few stock funds have ever outperformed the S&P500 over the long-term.

Probably a good general rule of thumb.

However it's possible that a fund with a bit of a sanity filter, or tilt towards actual value (not to be confused with the "value" factor as sold which is often just slow growth), might not be such a terrible thing. The performance you want to consider is from shortly before a bubble peaks till a year after the bear that follows. Things that are painfully overvalued don't rebound all the way back. A fund that merely underweights those things wouldn't be so bad.

Berkshire is interesting in that it has a history of not only bouncing all the way back to the prior level, but also bouncing all the way back to the prior trend. It participates heavily in one of my favourite aphorisms: you make most of your money during a bear market, you just don't realize it at the time.

A scary observation that might come in handy at some point in the next few years: if there is a bear market or a real melt down, there will be a bottom. It will probably be pointy: sharp final drop, sharp rebound. After some short period of time, the bottom in retrospect will seem pretty certain: everything is bouncing like a bungee. At that point, the stuff you want to own for a few months is the worst possible crap, the stuff that sold off the worst during the melt down, often deserving it. Think: meme stocks. The stuff that you would normally want to short. Defensives during the slide, speculatives for a couple/few months after the bottom, then prudent stuff.

Jim