RDS has historically added support for new mariadb releases within a year, but they seem stuck on 10.6 and haven't added the new 10.7, 10.8, 10.9, 10.10, 10.11, which are all GA.
MariaDB did change their policy and only provide 1 year support for most releases, the exception being 10.6 and 10.11 which are designated LTS. Was Amazon waiting for 10.11 and just haven't had enough time yet to release it?
Trying to make upgrade plans, but it's hard to do so without any information from Amazon on their plans.