If you are amongst the photographers who pre-order the latest and greatest cameras before they even ship then you know that dedicated L-brackets are usually delayed by many months, and companies such as RRS (Really Right Stuff), ProMediaGear and Kirk can hardly keep up with demand once they finally bring the new plates to market. In addition, sometimes their initial designs are not as successful as desired, and re-designs take them even longer. By the time that finalized designs are readily available, your next cameras are long announced, and all is back to square one.
There is, however, a solution, and that is to keep a couple universal L-brackets around, to bridge the wait for the dedicated brackets to ship. Without a stable, well crafted L- bracket, using the best flash brackets is an ordeal. To be sure, some lesser flash brackets can be used without an L-bracket, but the market leading system from RRS requires the L-bracket. I have used many types of flashes mounted directly to my cameras, ranging from Broncolor 3200Ws ring flashes to Quantum and various Flashpoint models, mainly the H1200 remote heads. I like to mix flash and available light in this way, sometimes using shutter drag techniques. Or sometimes it is just best to stay very mobile and forgo any stands or handheld lights by assistants.
Unfortunately, most universal L-brackets are not convenient or practical in design, and you will struggle with opening battery doors or connecting cables. Even companies that generally produce terrific gear, have only poorly designed universal L-brackets to offer, for example, Arca Swiss. Their L-Bracket is uncomfortable and gets stuck, and just is overall quite unusable. Do I really want to struggle with a hex key or some tight levers, only to change my batteries? In addition, this bracket also has sharp edges and is just a mess. Kirk makes a somewhat decent bracket, certainly usable, but with some flaws.
There is, however, a California company, Acratech, that makes a terrific (extended) L bracket for cameras with grips. The entire L is made out of one single aluminum piece, and not 2 pieces bolted together, which gives added stability. The integrated Arca-Swiss style Quick Release clamp can be also mounted in different orientations, one major advantage the Acratech has over the Kirk version. Personally, I like to space out the L quite far from the left side of the camera, for better access for tethering cables for example, but also for better grip.
In fact, this bracket feels so comfortable, that a dedicated bracket may not even be needed any longer in certain cases. I currently use the Acratech on my Fujifilm X-H1, a perfect combo, and just as nice as my dedicated RRS brackets for the larger Fujifilm GFX 50S.