W- salam
I was almost on same boat, my application received on 25 November 2020, got pre arrival in September 2022, since than stuck in background check, January 2024 i set all things ready to file mandamus and plan to submit on 12 Jan, its an expensive procedure, i took a chance to raise a web form one last time before mandamus and thank God just one day before on 10 January 2024 i got re medical request.
Medical done and update on 29 January, after i received several ghost update, on 19 February 2024 everything shows completed (including background check which was stuck for 17 months) on tracker.
Thank after 15 days 6th march 2024 a Copr number and approval of application update on tracker, now i am waiting for PPR.
My suggestion is for you first raise a web form directly to London visa office, and wait for 2 weeks, in web form you mention how this delay affects on your genuine relationship and mental health for both partners,
If still they don't reply or you didn't received any movement in your case than go for mandamus.
Hope this will help you.