I think precompilation is broken on Plots for 1.8 (not from a julia issue). This would lead to slower TTFP. See TTFP regression since 1.7 · Issue #44293 · JuliaLang/julia · GitHub, [FR] Enable precompilation for nightly · Issue #4079 · JuliaPlots/Plots.jl · GitHub, add version check for 1.8 precompiles by JeffBezanson · Pull Request #4179 · JuliaPlots/Plots.jl · GitHub
Edit: Actually the above is wrong. Precompilation is active for Julia 1.8 for Plots.jl and TTFP (for Plots.jl) is improved with about 15%.