QGIS3 - Clipping polygons to a hemisphere for azimuthal orthographic projection

You need to create a polygon with the shape of the globe in the orthographic projection to cut out the entities. That is what the solutions proposed, but with tools that are not updated to the new stable version of QGIS.

My idea is the following:

• Create a new vector layer of points with the custom orthographic CRS.
• Create a point in that layer. With Vertex Editor tool position it in coordinates 0 , 0.

• With Buffer tool, create a circle of 6371000m radius around the point. Use a good number of segments per quarter of a circle (90 segments form a polygon of 1 degree per side, you hardly notice the difference with a circle).
• Save the Buffered layer with the WGS84 CRS and load it to the canvas.
• Change the project CRS to WGS84.
• With the Difference tool, subtract between the layers you want to represent and the exported polygon.

• Save the Difference layers.
• Change the proyect CRS to the custom Orthographic system.

I had to eliminate the edge of the polygon of the sea because it went through the 180º longitude, in the symbology options of the layer.
Surely I am not using the same layers as you, but I do not think it is difficult to adapt the method to your layers. And the result is acceptable.