Would you consider D flat major a key to write in? You can find a few on Spotify: Sweet Child O'Mine, Appetite for Destruction. There's a long list of compositions on Wikipedia (vs songs). Concertos, scherzos, Waltzes, String quartets and then the lovely Clair De Lune by Claude Debussy. That fun Minute Waltz is in D flat major. Chopin liked D flat major.
There is Body and Soul. The Girl from Ipanema is another. A Nightingale Sang in Berkeley Square was sung in this key by Nat King Cole and Frank Sinatra.
The analysis of 30 million songs reveals that G major, C major, D major and A major account for one third of all songs. You can see the pie chart distribution of keys of all music on Spotify in the article HERE. It looks like D flat major doesn't show up on the chart. But what if there are D flat major (or minor) jokes. I did not find any, but there is a constantly repeating A flat minor joke:
What happens when you drop a piano down a mineshaft? A flat minor
And then we can find a lot of action in the extended version of the C E flat and G go into a bar joke:
C, E-flat, and G go into a bar. The bartender says, "Sorry, but we don't serve minors." So E-flat leaves, and C and G have an open fifth between them. After a few drinks, the fifth is diminished, and G is out flat. F comes in and tries to augment the situation, but is not sharp enough. D comes in and heads for the bathroom, saying, "Excuse me; I'll just be a second." Then A comes in, but the bartender is not convinced that this relative of C is not a minor. Then the bartender notices B-flat hiding at the end of the bar and says, "Get out! You're the seventh minor I've found in this bar tonight." E-flat comes back the next night in a three-piece suit with nicely shined shoes. The bartender says, "You're looking sharp tonight. Come on in, this could be a major development." Sure enough, E-flat soon takes off his suit and everything else, and is au natural. Eventually C sobers up and realizes in horror that he's under a rest. C is brought to trial, found guilty of contributing to the diminution of a minor, and is sentenced to 10 years of D.S. without Coda at an upscale correctional facility.
Time for a train day - these from Sacramento in 2019. I've given the layout "Blue Skies" - written in C Minor.
