New JMdict tag: [rK] rarely-used kanji form

[Thermospore]

Looks like there is a new JMdict tag which is getting a lot of usage:
http://www.edrdg.org/jmdictdb/cgi-bin/updates.py?svc=jmdict&sid=&y=2021&m=11&d=6

More of a yomichan import thing, but posting here cos this is where the activity is

[Thermospore]

looks like [rK] shows up in yomichan, but there isn't a way to distinguish which form it is referring to (in merged mode)