Making alcohol-free or low-alcohol beer that tastes good is actually really hard and is still actively being researched. Because of reasons, it’s even harder at homebrew scale.

The main methods are:

• biological method, aka arrested fermentation: low OG wort, ferment only briefly, then chill down hard to stop fermentation. Similar to what @[email protected] described. You can further reduce the amount of alcohol produced by selecting a maltose-negative yeast, such as Saccharomycodes ludwigii or a maltose-negative Saccharomyces cerevisiae strain, such as Lallemand LalBrew LoNa, which has only been released recently.
• physical method, aka dealcoholization: brew a normal strength wort, let it finish fermenting, then remove the alcohol through vacuum distillation or non-porous membrane distillation.

Each of the methods have their drawbacks. If you use a maltose-negative strain, you need to be able to pasteurize your beer, otherwise infections are inevitable. This is the reason why LalBrew LoNa is currently not sold to home brewers, as Lallemand does not think that home brewers will be able to reliable pasteurize and use the yeast correctly. The beer will also taste worty and sweeter than regular beer. Dealcoholization on the other hand is basically impossible to do at home. It also leaves behind a thin-tasting beer with unsatisfactory mouthfeel. Recent research has shown that the best tasting non-alcohol/low-alcohol beer can be produced by blending two beers made with these two methods.