These are all known pain points with AE 2026 and third-party plugins — you're not alone.
Bodymovin/Lottie issues in 2026 are almost certainly related to changes Adobe made to the rendering pipeline and how shape layers/gradients are processed internally. The Bodymovin extension reads AE's layer data directly, so any under-the-hood change Adobe makes can silently break export fidelity without Bodymovin throwing an error. The gradient black-and-white issue and missing trim paths are both reported by others on the Bodymovin GitHub — worth checking there and opening an issue if yours isn't already listed, as the maintainer is active.
Element 3D has historically always needed a version update after major AE releases — Video Copilot typically pushes a compatibility patch within weeks of a new AE version. Check their site directly for a 2026-compatible build, and in the meantime keep your AE 2025 install alongside 2026 for Element work specifically.
The practical advice for now: don't uninstall AE 2025. Running both versions in parallel is completely normal for production work and exactly the scenario Adobe's licensing allows for. Use 2025 for anything plugin-dependent until the third-party developers catch up, and use 2026 for native AE work.
Also worth checking — did you install the plugins fresh into 2026, or are you relying on the shared MediaCore/Common plugins folder? Some plugins need an explicit reinstall targeting the new version rather than inheriting from the shared path.