RFC 8446, "The Transport Layer Security (TLS) Protocol Version 1.3", August 2018

Errata ID: 6126
Status: Reported
Type: Editorial
Publication Format(s) : TEXT
Reported By: Ben Smyth
Date Reported: 2020-04-24

Section 4.1.1 says:

Note that if the PSK can be used without (EC)DHE, then
non-overlap in the "supported_groups" parameters need not be fatal, 
as it is in the non-PSK case discussed in the previous paragraph.

It should say:

Note that if the PSK can be used without (EC)DHE, then
non-overlap in the "supported_groups" parameters need not be fatal, 
as it is in the non-PSK case discussed in the previous paragraph, 
because PSK-only key exchange mode does not need supported_groups.

Notes:

If "the PSK can be used without (EC)DHE", then PSK-only key exchange mode can be used, which doesn't require supported_groups. This is perhaps worthy of explanation.

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