There are some common steps you need to repeat whenever you make Unity WebGL build or if you want to convert your project into WebGL. Beware I am not using Unity 2020.
Learn more: Unity WebGL Technical Breakdown
1. Convert to Latest Unity Version (if Possible):
Always try to use the latest Unity version if you are building for unity WebGL as unity WebGL has several issues. With each new unity release, we see different bug fixes but remember each new build brings it known issues. If you don't have any problem with the latest unity version then, you should adopt it for your WebGL project. Beware porting to your current project into the latest unity version can show significant compatibility issues, so make a backup before conversion.
2. Save Scripting Define Symbols
Before converting to WebGL please save your scripting define symbol outside unity (separately). Scripting defines symbols will be available under player settings. Some of the symbols are lost during WebGL conversion.
