Yes, the journal "Sustainability" by MDPI is still indexed in Scopus. The journal is also indexed in other databases like SCIE and SSCI (Web of Science), GEOBASE, and Inspec.
There is some confusion about the journal title. In your info you refer to a journal called “Sustainability” https://www.scopus.com/sourceid/16400154787 which is as you indicated continued under a new name https://www.scopus.com/sourceid/21101050033 but in both cases it is another publisher (Mary Ann Liebert).
Sustainability (Switzerland) is published (as you indicated in your question) by MDPI. This journal is indexed in Scopus https://www.scopus.com/sourceid/21100240100