The new Find a Tender Service is up and online - you can find it here. This replaces the OJEU website for tenders with a value above the relevant threshold, i.e. the larger public sector tenders. Note that any tender process that started on OJEU will be completed on OJEU and follow EU procurement rules. Just a reminder - the threshold values themselves have not changed this year - the current levels apply for 2020/1.
They appear to be calling it FTS, not FATS (as I rather hoped). It is not the easiest thing to find, but hopefully will be further up the listings on Google when it is bedded in a bit.
I have registered, and the process is fairly painless (not completely), and it IS linked to Contract Finder - which makes a lot of sense but was not guaranteed.