@Jasperx That was it. 25.12.0 and a very quick wireshark:
Ext Tag: Multi-Link (802.11be D3.0)
Ext Tag length: 15 (Tag len: 16)
Ext Tag Number: Multi-Link (802.11be D3.0) (107)
Multi-Link Control: 0x01b0 Basic
.... .... .... .000 = Type: Basic (0)
.... .... .... 0... = Reserved: 0x0
.... .... ...1 .... = Link ID Info Present: True
.... .... ..1. .... = BSS Parameters Change Count Present: True
.... .... .0.. .... = Medium Synchronization Delay Info Present: False
.... .... 1... .... = EML Capabilities Present: True
.... ...1 .... .... = MLD Capabilities Present: True
.... ..0. .... .... = AP MLD ID Present: False
.... .0.. .... .... = Extended MLD Capabilities and Operations Present: False
0000 0... .... .... = Reserved: 0x00
Link ID subfield: 0x01
BSS Parameters Change Count: 1
EML Capabilities: 0x0001, EMLSR Support
.... .... .... ...1 = EMLSR Support: True
.... .... .... 000. = EMLSR Padding Delay: 0
.... .... .000 .... = EMLSR Transition Delay: 0
.... .... 0... .... = EMLMR Support: False
.... .000 .... .... = EMLMR Delay: 0
.000 0... .... .... = Transition Timeout: 0
0... .... .... .... = Reserved: 0x0
MLD Capabilities: 0x2000, Link Reconfiguration Operation Support
.... .... .... 0000 = Maximum Number of Simultaneous Links: 0
.... .... ...0 .... = SRS Support: False
.... .... .00. .... = TID-To-Link Mapping Negotiation Support: 0
.... 0000 0... .... = Frequency Separation For STR/AP MLD Type Indication: 0
...0 .... .... .... = AAR Support: False
..1. .... .... .... = Link Reconfiguration Operation Support: True
.0.. .... .... .... = Aligned TWT Support: False
0... .... .... .... = Reserved: 0x0
EMLSR Support: True
EMLMR Support: False (This may never arrive)