I agree that there should be more engagement on this group. I am happy to offer support and advice in areas I am comfortable talking about.
The deadline for EUSS applications is 30 June 2021. However, it is still possible to apply after this deadline. Wait for your current leave to expire. A month or so before it expires, apply for settlement under EUSS (Appendix EU). Even if you apply after the deadline, they should still process your application. You seem to me to have a good excuse for filing late. If they refuse to accept your (late) application, appeal to the First Tier Tribunal.
Hope that helps!