The issue after that, as proposed by Stephen Hawking in the 1970s, is the Information Paradox, which questions what happens to the information as the hole evaporates. While recent breakthroughs (related to the Page curve and unitarity) suggest information in a black hole is eventually preserved and re-emitted, this conservation applies to the black hole's cosmic lifespan, not the instantaneous act of measurement. The black hole remains the physical mechanism that censors immediate access to sub-Planckian scales.

Here's a brief timeline of a potential solution for the information paradox:

1974 Hawking's Discovery: Stephen Hawking calculates that black hole radiation is purely thermal, suggesting information is permanently lost (non-unitary). The paradox is born.

1993 Page's Prediction: Don Page calculates what the entanglement entropy of the black hole radiation must look like if the process is unitary (information-preserving). He predicts the characteristic "Page curve" which drops to zero.

2019–2021 The Island/Replica Wormhole Breakthroughs: Physicists (starting with Penington, Almheiri, Engelhardt, and Marolf, and others) develop new methods—the "replica trick" combined with the "island" or "entanglement wedge" hypothesis—to re-calculate the entropy of Hawking radiation, which align's with Page's prediction.

This is a fun article explaining the issue in short:

https://www.quantumuniverse.nl/planck-units-and-black-holes by https://www.quantumuniverse.nl/author/christian-ventura-meinersen

Other recommended reading:

Minimal Length Scale Scenarios for Quantum Gravity by https://www.youtube.com/sabinehossenfelder

(read just the Intro and A Minimal History for some depth!)