Not currently. Rendering is provided by the wgpu library, which wraps vulkan/directx12/directx11/webgpu/metal/opengl es/webgl2. No webgl1 support. If wgpu gained webgl1 support in the future then bevy would too, but it's unlikely imo. Webgl2 is already extremely limiting as it is (no storage buffers/textures, no compute passes).

What is your use case for needing webgl1?

Bevy is also extremely modular. If you absolutely need webgl1 support, you can implement it yourself as a plugin without losing the rest of the non-rendering parts of bevy like audio, input, the core ECS of course, etc.