Buster uses libsearch-elasticsearch-perl 6.00-1 as default https://packages.debian.org/buster/libsearch-elasticsearch-perl We should backport this package to stretch, and set 6.00-1 as the default fyi, currently buster ES tests fail, as Koha defaults to v5 but v6 is installed koha_1 | Test Summary Report koha_1 | ------------------- koha_1 | t/db_dependent/Koha/SearchEngine/Elasticsearch/Search.t (Wstat: 512 Tests: 4 Failed: 0) koha_1 | Non-zero exit status: 2 koha_1 | Parse errors: Bad plan. You planned 13 tests but ran 4. koha_1 | t/db_dependent/Koha/SearchEngine/Elasticsearch/Indexer.t (Wstat: 65280 Tests: 2 Failed: 1) koha_1 | Failed test: 2 koha_1 | Non-zero exit status: 255 koha_1 | Files=484, Tests=10443, 2797.37 wallclock secs ( 4.77 usr 4.35 sys + 1572.95 cusr 561.96 csys = 2144.03 CPU) koha_1 | Result: FAIL
*** This bug has been marked as a duplicate of bug 24552 ***