People running servers don't seem to be reliably capable of making sure that either pMTUd works or isn't needed on their network, so... it is indeed broken on random servers.
We've mostly decided to go with TCP MSS clamping rather than using the minimum MTU, which is still nonsense but it's nonsense that we already decided to go with for the same problem in v4.
Of course, I don't have enough info to tell if this was the problem or if it was something else, or a mix of the two, but pMTUd does seem to be a leading cause of "fails to load for some weird reason" problems.
We've mostly decided to go with TCP MSS clamping rather than using the minimum MTU, which is still nonsense but it's nonsense that we already decided to go with for the same problem in v4.
Of course, I don't have enough info to tell if this was the problem or if it was something else, or a mix of the two, but pMTUd does seem to be a leading cause of "fails to load for some weird reason" problems.