Ancient cities and trial chambers can intersect.
Seed: 8879501418461304687
Coordinates: /execute in minecraft:overworld run tp @s 14484 -38 -9464 -123 11Relates to:
Ancient city intersections
Trial chamber intersections
Misc
[MC-266586]: May make these intersections more likely, but a fix would not eliminate the issue since structures can (and do) intersect ancient cities after beginning their generation from outside the deep dark.
[MC-266446] doesn't quite meet the criteria for issue relation but is worth keeping an eye on, since if it were fixed, the nature of the trial chamber-ancient city interaction could be affected, potentially negatively.
Can confirm: check the two attached screenshots.
It's important to note that the 1.21 experimental features must be enabled for the stronghold to be visible, otherwise the structure won't actually generate in its intended location. You can verify its spawn location otherwise by running the /locate command in a world created without enabling the experimental features.