Toboe_Irbis pointed out, that a similar bugpost has been fixed properly: MC-161297
Shulkerboxes were exempt from not being rendered, so a similar fix should be doable for end gateways.

As we Creative contraption makers find good use in end gateways being rendered if a player stands inside them, e.g. in "Stargates", I'd like to ask Mojang to please reconsider fixing this bugpost properly, and not having it stay resolved as "works as intended", unless there are other good reasons why gateways shouldn't be rendered for a player inside.

Thank you.

Discussions about this bugpost go here:
https://www.reddit.com/r/Mojira/comments/f1vv8q/mc163023_marked_as_wai
_{Side note: It is currently unknown if this bugpost was resolved as WaI due to a limitation of the new rendering engine, thus the above appeal on the Mojira Subreddit to have this bugpost reopened may be futile after all, at least at the current state of code, but it'd be nice to have a developer stating this, so contraption makers can try to come up with a workaround, and not waiting for this bug to be fixed as desired.}

The bug

When a player stands inside an end gateway block, which does not teleport them (ExitPortal is not set), its texture does not render, as it was previously the case.

Tested in Creative- as well as Survival-mode.

To reproduce

Setblock an end gateway, e.g. with

/setblock ~ ~1 ~ end_gateway

Videos

1.14.4: https://www.youtube.com/watch?v=okjCmAkDkhw
1.15.2: https://www.youtube.com/watch?v=upBY4YxgYQ4