I was able to set the innodb parameters only after having rolled back vm.overcommit_memory to 0.
Soon after the mariaDB changes the memory situation is:
MiB Mem : 7665.7 total, 2131.7 free, 1833.2 used, 3700.8 buff/cache
MiB Swap: 2048.0 total, 1937.8 free, 110.2 used. 5033.2...