I am using Nextcloud via docker containers, I was not specifying the image version of mariadb in my docker-compose.yml and ran into the problem mentioned in this thread.
Solved easily by adding version 10.5 for mariadb image in the docker-compose.yml:
nextclouddb:
image: mariadb:10.5
MariaDB 10.5 LTS runs until 24 Jun 2025 - so long time left to solve the issue!