It's probably the main camera.... Play with the main camera settings..... Turn from base... To overlay should work..... Then back to base if you want base.......... and turn sky box ... Options in main camera settings to color.... Should work.... Worked for me

some related discussions posts i found:
https://discussions.unity.com/t/commandbuffer-temporary-render-texture-not-found-while-executing-setrendertarget-depth-buffer/870063/22

https://discussions.unity.com/t/commandbuffer-built-in-render-texture-type-3-not-found-while-executing/949029

Reproducible with 6000.2.0b7 and 6000.2.0b8 as well, caused by render graph (why does Gizmo rendering require depth buffers, anyways?)

warning thrown in com.unity.render-pipelines.universal@0ace31fce978 from ScriptableRenderContext:Submit() at Runtime/UniversalRenderPipeline.cs:893 (UniversalRenderPipeline:RenderSingleCamera)

Reproducible with 6000.1.10f1 and I confirm that disabling Gizmos on Game tab makes the error go away

Reproducible with 6000.0.51f1 and 6000.0.47f1 when using URP and the new Render Graph API in an empty project while the Game window renders new frames with Gizmos enabled.

If the game window is hidden or gizmos are disabled the warning isn't shown

(Disabling render graph API by using URP compatibility mode in Edit > Projects Settings > Graphics > Graphics > Render Graph fixes the issue)

I also tried 6000.0.49, 6000.1.0f1, 6000.1.4f1
and then even the beta version: 6000.2.0b2.
Problem is there in every version as said earlier.

I found another one regarding similar warning:
https://issuetracker.unity3d.com/issues/urp-commandbuffer-built-in-render-texture-type-3-not-found-while-executing-warning-is-thrown-when-game-view-is-open-and-opengl-is-used

I am able to reproduce this bug in 6000.0.47, 6000.0.48, 6000.0.49, and all versions of 6000.1.x.

Just create a new URP project and enable gizmos within game view.