I'm filing this now as a bit of a placeholder and will add detail.
GitLab 14.x has been out since June, and further updates to the 13.x line aren't planned unless major issues come up.
We should get a sense of whether 14.x is stable enough to upgrade to at this point and plan / test our upgrade.
cc: @Jelto, @thcipriani, @MoritzMuehlenhoff.
This is also probably of interest to @jeena as, based on some exploration of features, it might affect how usable GitLab is for the planned preview environment stuff.