Discovered while testing MC-239268.

The bug

The end portal and end gateway blocks use the default "stone" breaking sound. This is unlike the nether portal, which uses glass sounds instead.

How to reproduce

1. Break a nether portal block in Creative mode (can be placed via /setblock ~ ~ ~5 minecraft:nether_portal), and note how it uses the glass sound
2. Break an end portal block in Creative mode (can be placed via /setblock ~ ~ ~5 minecraft:end_portal), and note how it uses the stone sound
3. Break an end gateway block in Creative mode (can be placed via /setblock ~ ~ ~5 minecraft:end_gateway), and note how it uses the stone sound

Expected behaviour

Either end portals and end gateways would use the glass sound for consistency with nether portals, or (possible feature request territory) a new dedicated set of "portal" block sounds would exist, with the breaking sound being analogous to the opening of an end portal.

Actual behaviour

End portals and end gateways use the stone sound, a default for all blocks.

Notes

This was one of the cases listed in MC-91091, a ticket which has since been resolved as Invalid. As the consensus on the bug tracker seems to be grouping issues like these together is a very bad idea, I am re-reporting this separately, as has been done for many other issues listed there, for a fair retrial.